Annual Report 2001

2001 NATIONAL INSTITUTE FOR NUCLEAR PHYSICS AND HIGH-ENERGY PHYSICS

ANNUAL REPORT 2001

Kruislaan 409, 1098 SJ Amsterdam P.O. Box 41882, 1009 DB Amsterdam Colofon

Publication edited for NIKHEF: Address: Postbus 41882, 1009 DB Amsterdam Kruislaan 409, 1098 SJ Amsterdam Phone: +31 20 592 2000 Fax: +31 20 592 5155 E-mail: [email protected] Editors: Louk Lapik´as & Marcel Vreeswijk Layout & art-work: Kees Huyser Organisation: Anja van Dulmen Cover Photograph: A 3-D drawing of the LHCb Vertex detector URL: http://www.nikhef.nl

The National Institute for Nuclear Physics and High-Energy Physics (NIKHEF) is a joint venture of the Stichting voor Fundamenteel Onderzoek der Materie (FOM), the Universiteit van Amsterdam (UVA), the Katholieke Universiteit Nijmegen (KUN), the Vrije Univer- siteit Amsterdam (VUA) and the Universiteit Utrecht (UU). The NIKHEF laboratory is located at the Science and Technology Centre Watergraafsmeer (WCW) in Amsterdam.

The activities in experimental subatomic physics are coordinated and supported by NIKHEF with locations at Amsterdam, Nijmegen and Utrecht. The scientiﬁc programme is carried out by FOM, UVA, KUN,VUAandUUstaﬀ.Experimentsaredone at the European accelerator centre CERN in Geneva, where NIKHEF participates in two LEP experiments (L3andDELPHI),inaneutrino experiment (CHORUS) and in SPS heavy ion experiments (NA57 and NA49). NIKHEF participates in the Tevatron experiment D0 at Fermilab, Chicago. At DESY in Hamburg NIKHEF participates in the ZEUS, HERMES and HERA-B experiments. Research and development activities are in progress for the future experiments ATLAS, ALICE and LHCb with the Large Hadron Collider (LHC) at CERN.

NIKHEF is closely cooperating with the University of Twente. Training and education of students are vital elements in the research climate of the laboratory. Contents

Preface 1

AExperimental Programmes 3

1AmPS 3 1.1 Introduction 3 1.2 Experiments at EMIN 3 1.3 Experiments abroad 6

2TheAntaresProject 9 2.1 Introduction 9 2.2 Progress in 2001 9 2.3 Recent developments 10

3TheATLASExperiment 11 3.1 Introduction 11 3.2 D0 experiment 11 3.3 ATLAS experiment 12 3.4 ATLAS detector R&D spin-oﬀ 15

4B-physics 19 4.1 Introduction 19 4.2 HERA-B 19 4.3 LHCb Outer Tracker 21 4.4 LHCb Vertex detector 23 4.5 LHCb front-end chip 26 4.6 L0 Pile Up Veto System 27 4.7 Track Reconstruction 28 4.8 LHCb Physics Performance 30

i 4.9 Grid Activities 30

5CHORUS 33

6HeavyIonPhysics 35 6.1 Introduction 35 6.2 Direct photons in WA98 35 6.3 Strange baryon production in NA57 36 6.4 Strangeness and Charm Production in NA49 37 6.5 The Alice experiment 39

7HERMES 41 7.1 Introduction 41 7.2 Physics analysis 41 7.3 The JLab experiment 45 7.4 The Lambda Wheel project 45 7.5 Longitudinal Polarimeter 46 7.6 Outlook 47

8ZEUS 49 8.1 Introduction 49

8.2 Structure Function F2 49 8.3 Micro-Vertex Detector 50

BLEP in 2001 53

1DELPHI 53 1.1 End of data taking and reprocessing 53 1.2 Selected research topics 53 0 − 0 1.3 Bd Bd oscillations 53 1.4 W mass and width 54 1.5 ZZ cross section 54 1.6 Flavour blind Higgs search 55

2L3 57 2.1 Introduction 57 2.2 Searches 57 2.3 Fermion pairs 58

ii 2.4 W physics 58 2.5 QCD 60 2.6 L3+Cosmics 60

CTheoreticalPhysics 61

1Theoretical Physics Group 61 1.1 Particles, ﬁelds and symmetries 61 1.2 Research program 61 1.3 Teaching 62

DTechnical Departments 63

1Computer Technology 63 1.1 Introduction 63 1.2 Central services 63 1.3 Network infrastructure 63 1.4 Security 64 1.5 Desktop systems 64 1.6 Farm conﬁgurations 64 1.7 Amsterdam Internet Exchange (AMS-IX) 64 1.8 Software engineering 65 1.9 ANTARES 65 1.10 Embedded software for ATLAS hardware modules 65 1.11 Communication between Trigger/ DAQ and DCS in ATLAS 66 1.12 Applications for the production of ATLAS muon chambers 66

2Electronics Technology 69 2.1 Introduction 69 2.2 Projects 69 2.3 Department development 74

3Mechanical Workshop 75 3.1 Introduction 75 3.2 Projects 75

4Mechanical Engineering 79 4.1 Introduction 79

iii 4.2 Running Experiments 79 4.3 Projects in development 79

5GridProjects 83 5.1 Introduction 83 5.2 DataGrid 83 5.3 AliEn 85 5.4 D0 Grid 85 5.5 DataTAG 85

6Future Projects: TESLA 87 6.1 Introduction 87 6.2 Physics Motivation 87 6.3 Detector R&D 87 6.4 Investigation into a beam protection system for TESLA 88

EPublications, Theses and Talks 89

1Publications 89

2PhDTheses 97

3InvitedTalks 98

4SeminarsatNIKHEF 102

5NIKHEF Annual Scientiﬁc Meeting December 13-14, 2001, Amsterdam 104

FResources and Personnel 105

1Resources 105

2Membership of Councils and Committees during 2001 106

3Personnel as of December 31, 2001 107

iv Preface

In this Annual Report we look back at the achievements During the first six months of the period covered by this of NIKHEF in the year 2001, a year that unfortunately annual report the NIKHEF programme was carried out wasovershadowed by the tragic death of Cees Bakker under the responsibility of my predecessor professor Ger who we commemorate with thankfulness. van Middelkoop. It was a rewarding tasktoconsolidate this ambitious and well balanced programme in a well In theyear 2001 important progress was made towards organised institute with an excellent infrastructure. I the technical realisation of the large-scale hardware proj- hope that the fruitful collaboration in NIKHEF between ects for the future LHC experiments. The production of FOM and the universities KUN, UU, UvA and VU will the Atlas muon-chambers was successfully started and continue to proof an excellent basis for research at the the first vacuum vessel of the huge end-cap toroids was frontier ofoneofthemost exciting fields in physics - produced in industry and delivered at CERN. The de- afieldinwhichimaginative attempts to look beyond velopment and production of the state-of-the art instru- the horizon of the LHC already appear on the agenda; mentation for Atlas, LHC-b and Alice will continue to NIKHEF certainly has the ambition to also participate make great demands on the professional skills and ded- in the definition of this agenda and with our priorities ication in our technical departments during the coming clearly reflected in this Annual Report 2001 I hope we years. As has been the case in 2001 we will have to will have a lively scientific debate even beyond these solve complex technical and planning problems within priorities. tight constraints imposed by limited resources – I am convinced we will be able to do so, motivated by the fact that the LHC is the most important project in high energy physics on a world-scale for at least the coming decade. Computing in the LHC era will put unprecedented demands on CPU and storage capacity. NIKHEF plays a leading role in various pilot projects Jos Engelen aiming at developing GRID technology, the new approach to large scale computing. Wonderful results continue to emerge from the Del- phi and L3 experiments at LEP and from ZEUS and Hermes at HERA. The latter two have undergone major upgrades in 2001 with important contributions from our institute. These experiments and also the HERA-B experiment at DESY (Hamburg, Germany), the fixed target heavy ion experiments at CERN and the D0 project at Fermilab (Batavia, USA) will provide excellent opportunities for research at the forefront of high energy physics while the LHC programme is prepared. In 2001 the Chorus programme was concluded; a num- berofinteresting publications will, however, still follow as is the case for the AmPS programme concluded earlier. The Antares project in the emerging new field of astro-particle physics made important steps towards the launch of the first detector string in the Mediterranean Sea, now planned for late 2002. The NIKHEF partic- ipation in Antares represents the only activity in the Netherlands in this rapidly growing field. 1 2 AExperimental Programmes 1AmPS

1.1 Introduction components strongly depend on p and are sensitive to the repulsive core of the NN interaction at short dis- The analysis of the experiments performed with AmPS tances. To obtain sensitivity to the spin structure of the reaches its final stage. While the analysis of all exper- deuteron, spin-dependent observables in quasi-elastic iments carried out in EMIN is finished, there remain scattering can be used. In the 2H(e, e p)n reaction, an the analyses of a few experiments performed in the energy ω and a three-momentum q are transferred to Internal-Target Facility (ITF). These pertain to scat- the nucleus and the nuclear response can be mapped as tering of polarised electrons off polarised 1H, 2Hand afunction of missing momentum p and missing en- 3He targets. m ergy. In the plane-wave impulse approximation (PWIA) The electron-scattering programme with AmPS has the neutron is only a spectator during the scattering been concluded with a report Results of the AmPS process, and pm is equal to the initial proton momen- Program submitted early 2001 to the funding agency tum in the deuteron, while the missing energy equals FOM. In this report an overview is given of the physics the binding energy. program carried out at the electron-scattering facility The polarisation of a proton Pp inside a deuteron with AmPS at NIKHEF in the period 1992-1998. The re- z avector polarisation Pd ,isgivenby port describes the instrumentation built for this pro- 1 gram, and the results obtained with the extracted beam in the EMIN hall and with the stored (polarised) beam p 2 d − 1 Pz = P1 PS PD , (1.1) in the internal target facility. The scientific program at 3 2 AmPS was subjected to continuous review by an international Program Advisory Committee (PAC) that met where PS and PD represent the S-andD-state prob- five times between 1991 and 1997. In this period the ability densities of the ground-state wave function, re- PAC has considered about 50 proposals, of which 25 spectively. Note that the polarisation of a nucleon in were approved for running. The total amount of beam the D-state is opposite to that of a nucleon in the S- time spent on data taking for these proposals was 4900 state. hours in EMIN and 3400 hrs in ITF. About 40 groups The cross section for the 2H (e, ep)n reaction,inwhich from abroad haveparticipated in the research program longitudinally polarised electrons are scattered from a with the beams from AmPS. Part of this work took polarised deuterium target, can be written as place within the framework of European network collaborations. The AmPS program has yielded about 60 S = S { 1 + Pd AV + Pd AT publications in refereed journals and 35 theses. 0 1 d 2 d d V d T } + h ( Ae + P1 Aed + P2 Aed ) , (1.2) 1.2 Experiments at EMIN

Spin-Momentum Correlations in Quasi-Elastic Elec- where S0 represents the unpolarised cross section, h the d d tron Scattering from Deuterium polarisation of the electrons, and P1 (P2 )thevector (Prop. 97-01; with ETH, Virginia, Arizona, TJNAF, (tensor) polarisation of the target. The beam analysing MIT, Hampton, Novosibirsk) V /T V /T power is denoted by Ae ,withAd and Aed the vector and tensor analysing powers and spin-correlation pa- The deuteron serves as a benchmark for testing nuclear rameters, respectively. We report on the ﬁrst measure- theory. Its simple structure allows reliable calculations ment of AV in the 2H (e, ep)n reaction. to be performed in both non-relativistic and relativistic ed frameworks. Such calculations are based upon state- Fig. 1.1 shows the experimental results in comparison of-the-art nucleon-nucleon (NN)potentialsandthere- to various predictions. The short-dashed and dot-dot- sulting ground-state wave function is dominated by the dashed curves are PWIA predictions for the Argonne v18 S-state, especially at low relative proton-neutron mo- NN potential with and without inclusion of the D-state, mentum p in the centre-of-mass system. Due to the respectively. The ﬁgure shows that inclusion of the D- tensor part of the NN interaction a D-state component state is essential to obtain a fair description of the data is generated. Models predict that the S- and D-state for the higher missing momenta. The other curves are

3 V all models underestimate Aed .Thismaybeattributed to an underestimate of the D-state contribution or to a lack in our understanding of the eﬀects of ∆-excitation. 0.2 This observation may be related to the deﬁciency in the prediction of the deuteron quadrupole moment by modern NN potentials.

ed The present data comprise the first-time results for the A ◦ ◦ V spin correlation parameter AV (90 , 0 ) in quasi-elastic 0 ed electron-proton knock-out from the deuteron. The data PWIA (S only) are sensitive to the effects of the spin-dependent mo- PWIA (S+D) NORMAL mentum distribution of the nucleons inside the deuteron. N+MEC The experiment reveals in a most direct manner the ef- -0.2 N+MEC+IC fects of the D-state in the deuteron ground-state wave FULL function and shows the importance of isobar configurations for the 2H (e, ep)n reaction. 0 100 200 300 400 Spin-Dependent Electron-Proton Scattering in the Pm [MeV/c] ∆-Excitation Region (Prop. 97-01; with ETH, Virginia, Arizona, TJNAF, MIT, Hampton, Novosibirsk) Figure 1.1: Spin correlation parameter AV (90◦,0◦)as ed Pion production in the ∆-resonance region is dominated afunction of missing momentum for the 2H (e, ep)n by the magnetic dipole transition form factor (M1). reaction at Q2 = 0.21 (GeV/c)2.Theshort-dashed Polarisation experiments have established the presence and dot-dot-dashed curves are PWIA predictions for of small but non-zero quadrupole components (E2and the Argonne v NN potential with and without in- 18 C2). In the present 1H (e, e) experiment, we have mea- clusion of the D-wave, respectively. The other curves sured for the first time both longitudinal and transverse are predictions of the model of Arenhövel et al., spin correlation parameters in the ∆-region, which are for PWBA+FSI (dotted), PWBA+FSI+MEC (dashed- sensitive to the E2 and C2formfactors,respectively. dotted), PWBA+FSI+MEC+IC (long-dashed) and In order to reliably associate the data with this subtle FULL calculations which include relativistic corrections feature of baryon structure, models, such as the MAID (solid). The predictions are folded over the detector model and the model of Sato and Lee, are required acceptance by using a Monte-Carlo method. that can accurately describe the reaction mechanism of γ∗p → πN and that are able to disentangle resonant fromnon-resonant contributions. predictions of the model of Arenhövel et al. for the Bonn NN potential and with different descriptions for The experiment was performed with polarised electrons, the spin-dependent reaction mechanism. accelerated to 720 MeV and stacked in the AmPS storage ring in which a polarised gas target was po- V At pm < 100 MeV/c,thetheoretical results for Aed sitioned. The scattered electrons were detected in a neither depend on the choice of the NN potentials, nor large-acceptance magnetic spectrometer. The polar- on the models for the reaction mechanism. This shows isation axis of the target was oriented, by means of that in this specific kinematic region the deuteron can amagnetic holding field, parallel or perpendicular to be used as an effective neutron target. For increas- the direction of the central momentum transfer for ing missing momenta, both the data and predictions W = 1232 MeV. for the asymmetry reverse sign. This is expected from Eq. (1.1) for an increasing contribution from the D- To compare the theoretical results to the data, we state component in the ground-state wave function of developed a Monte-Carlo (MC) code that folded the the deuteron. It can also be observed that inclusion model predictions over the acceptance. Radiative ef- of reaction-mechanism effects, mainly isobar configura- fects were taken into account by incorporating the fully tions, are required for a better description of the data. spin-dependent code POLRAD. Figure 1.2 shows the event distribution as a function of invariant mass in In the region of pm around 200 MeV/c where the S- comparison with the MC simulation using the MAID and D-states strongly interfere, the data suggest that

4 ] ∆ ∆

< 2> [ 2 2] a) q 0.2 b) ||q E2/M1 C2/M1

Q GeV /c ⊥ A 0.4 +2.2% A +0.0% 0.14 0.12 0.10 5 1 -0.1% -7.9% 10 -2.2% -13% Events nbarn MeV sterad

0.2 0

[ 0.5 Ω σ

2 0 0 d dE'd 1.1 1.15 1.2 1.25 10 4 -0.2 -0.2 0.2 0.1 sys δ -0.4 0.1 -0.4

3 sys 10 δ -0.6 -0.1 -0.1 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 0.9 1 1.1 1.2 1.3 0.9 1 1.1 1.2 1.3 Invariant mass W [GeV] Invariant mass W [GeV]

Figure 1.2: Event distribution as a function of W (see Figure 1.3: Preliminary results for the spin correlation text for explanation). parameters for longitudinal (a) and transverse (b) spin kinematics as a function of invariant mass W . The dashed curves represent the Sato and Lee model pre- model. The target density was determined by normal- dictions. The other curves indicate predictions of the ising the MC results to the data in the region of the MAID model for different quadrupole strengths (see elastic peak (open circles). The dotted and dot-dashed text for explanation). curves show the contributions from elastic and pion- production processes (including radiative effects). The insert shows the cross section extracted from our mea- experiment with polarised electrons and polarised 3He. sured rates after subtracting the elastic radiation tail As the two protons are in a relative S state for 90% and correcting for radiative effects. On top the average of the 3He ground state wave function, polarised 3He 2 Q for each W bin is shown. The shaded area repre- can be used as an effective polarised neutron target. sents the size of the systematic uncertainty. The results The Ax asymmetry in the (e, e n) reaction channel is are consistent with the cross section of the MAID model n of order 0.1 and sensitive to GE ,theelectric form factor (solid curve) and Sato and Lee model (dashed curve). of the neutron. The Az asymmetry is of order 0.5 and The two spin correlation parameters are shown as a mainly used as a benchmark for the theoretical models function of the invariant mass W in Fig. 1.3. The and for possible systematic errors in the experiment. asymmetry data were normalised to the predicted value In 2001 the background contributions were reanalysed in the elastic region (open circles). The systematic er- and found to be significantly larger than previously es- rors δsys areindicated by the shaded area. The models timated. A remaining unexplained correlation of the Az describe reasonably well the global behaviour of the asymmetry with the beam current has been translated present spin correlation data. into a systematic error, which turned out to be of the The agreement between the models and the data may same order of magnitude as the statistical error. be improved by adjusting the quadrupole strengths, For the kinematics in our experiment (Q2 ≈ 0.2GeV2/c2) which are relatively unconstrained model parameters. Final-State Interactions (FSI) are expected to play an The solid curves indicate the best fits for E2/M1and important role. Calculations were carried out by the − C2/M1usingtheMAIDmodel(E2/M1 = 0.1% and Bochum theory group of J. Golak and by S. Nagorny, − C2/M1 = 7.9%). The predictions of the Sato and using fundamentally different formalisms. Golak’s cal- − − Lee model (E2/M1 = 2.0% and C2/M1 = 4.2%) culations are based on a non-relativistic formalism which are indicated by the dashed curves. takes FSI into account to all orders by solving a set of Polarisation observables in 3He (e, en) Faddeev equations. Nagorny’s Lorentz covariant calcu- (Prop. 94-05; with ETH, Virginia, Arizona, TJNAF, lations include rescattering terms up to second order. n MIT, Hampton, Novosibirsk) Both methods use GE as a free parameter. In the Internal Target Hall of the MEA/AmPS electron The final results of the Monte-Carlo simulations based accelerator facility we performed an electron-scattering on these calculations became available in 2001 (see Fig.

5 0.2 1000 3 He(e,e'pn) Spn = 7 MeV

800 0.1

600 x ' 0 A

counts 400 7 MeV FWHM

-0.1 200

-0.2 0

-200 -150-100-500 50 100 150 -0.3 050100 150 200 250 Em [MeV] Pm [MeV/c] Figure 1.5: Missing energy spectrum of the 3He(e, e pn) reaction.Thepeak corresponds to the Figure 1.4: The Ax asymmetry versus missing momentum. The curves are results of Monte-Carlo simulations transition in which the residual system is left in its n ground state. based on Faddeev calculations with GE = 0 (dotted) or n equal to the Galster parameterisation GE,Galster (solid), and on the calculations by Nagorny, with G n = 0 (dash- E ing data of the complementary 3He(e, epp) reaction, dotted) or G n = G n (dashed). E E,Galster obtained at AmPS. This approach offers the unique possibility to directly compare the relative importance of pp and pn correlations, as well as the contribution 1.4). The MC results based on Nagorny’s calculations of isobar and meson-exchange currents, in the three- do not show a large deviation from the lowest-order cal- nucleon system. culation (plane-wave impulse approximation), whereas During a first beam time period data were taken at a the Faddeev calculations exhibit a large negative offset momentum transfer q = 375 MeV/c and an energy due to FSI. This negative offset is compatible with our transfer ω = 220 MeV. The scatteredelectrons were n ± experimental Ax data for a GE value of +0.031 0.034 detected in the magnetic Spectrometer B. Proton de- (the purely statistical error is 0.023). Using Nagorny’s tection was performed with the highly segmented scin- n calculations one would extract a negative value for GE tillator array HADRON3, while the neutrons were de- which is inconsistent with the world data set by four tected in a time of flight unit (TOF) placed opposite standard deviations. to HADRON3. 1.3 Experiments abroad After the accomplishment of the single-arm calibra- Study of the 3He(e, epn) Reaction tions of the HADRON3 detector, the electronic life- (Prop. A1/4-98; with the Universities of Mainz, Tübingen times of the front ends have been determined and tim- and Glasgow) ing calibrations have been performed. After all corrections are applied on the data, the timing resolution Nucleon-nucleon correlations and two-body currents in achieved for electron-proton coincidences amounts to the three-nucleon system are under investigation by 1.1 ns (FWHM). means of a 3He(e, epn) experiment in the A1 hall at MAMI, Mainz. This nucleus has been chosen because The implementation of the HADRON3 analysis code continuum-wave Faddeev calculations with realistic NN in the software package COLA, traditionally used by interactions are presently available. The interpretation the A1 collaboration, has been accomplished. A first of these data will be done in combination with the exist- version of the Monte-Carlo simulation of the detection

6 volume in phase space has also been implemented in the package for this detector. Finally, a procedure to evaluate and subtract the contribution of accidental coincidences is under development. The TOF detector provides a wide window for the arrival time of the neutron. Therefore the neutron spectra are dominated by accidental events. In the two- fold time-difference distribution, electron-proton versus electron-neutron time differences, regions are allocated where the various types of accidental coincidences contribute. These contributions must be properly normalised and subtracted during data analysis. After subtraction of accidental coincidences the missing energy spectrum, as shown in Fig. 1.5, is obtained. Here, the peak at Em=7 MeV with a resolution of 7 MeV (FWHM) corresponds to the transition in which the residual system is left in its ground state, which in the case of 3He(e, epn),isthe recoiling proton. It represents the first observation of a discrete transition in the reaction (e, epn). The combination of the results provided by the simulation and the data analysis is in progress in order to obtain the experimental cross section corresponding to the 3He(e, ep) and 3He(e, epn) reactions.

7 Antares, a neutrino telescope at the bottom of the Mediterranean Sea (Artist impresssion).

8 2TheAntaresProject

2.1 Introduction data filtering. Data buffering allows us to correlate events with (delayed) information from another obser- The current Antares detector is designed to comprise vatory (e.g. a Gamma-Ray-Burst warning). 1000 photo-multipliers (PMs) protected from the am- bient water pressure of 250 atm by spherical glass con- 2.2 Progress in 2001 tainers. The PMs are arranged in triplets, attached In May 2001 the Antares collaboration completed a at 12 m vertical inter-triplet distance to strings with a Technical Design Report, stipulating the choices for the length of about 500 m. These strings, anchored on the technical implementation of the detector (optical mod- sea bed and kept vertical by a buoy, will be positioned at ules, front-end electronics, timing and position calibra- adepth of 2500 m in the Mediterranean sea, 40 km off tion and monitoring, readout and optical fibre com- the coast near Toulon. The Cerenkovˇ light associated munication, electrical power generation and distribu- with muons originating from charged-current neutrino tion, geometrical layout of the detector, infrastructure, interactions in or near the active volume of the detec- launching and deployment procedures). The objective tor (0.1 km2×0.5 km) is detected by the PMs. The of the next major milestone of the Antares project is arrival times of the photons are measured with better to launch a prototype sector line consisting of 5 PM than 1 ns accuracy with the help of synchronous off- triplets and comprising all of the essential prototype shore (slave) clocks driven from shore by a master clock technologies of the detector. This prototype corre- that is coupled to the Global Positioning System. Tim- sponds to 1 of a completely equipped line. ing accuracy combined with position information of the 6 PMs to better than 20 cm yields an angular resolution In 2001 progress has been achieved by the Collaboration of the reconstructed muon track (and hence the neu- in the following areas : trino track) of 0.2◦. Whilst the cosmic neutrino spectrum above a few tens • The master-slave clock system with a realistic lay- of MeV (below this energy range there are e.g. the out of the optical fibre network was measured to solar neutrinos) is unknown, the existence of charged- have a time jitter of better than 500 ps FWHM, particles in cosmic rays with energies from 109 eV up to well within specifications. Long-term stability ap- 1021 eV suggests the existence of high-energy cosmic pearstobeadequate. neutrinos of similar energies. Angular resolution is a • crucial parameter for the detection of cosmic neutrino Installation of the acousticpositioning system off- point sources, such as gamma-ray burst sources and shore and validation of acoustic positioning accu- galactic micro quasars: looking for a neutrino signal racy in situ. in a given direction and time interval implies a back- • ground free observation. In general, due to the light- Submarine target-site validation. Adequate flat- propagation characteristics of water, underwater neu- ness of sea bed and absence of major obstacles trino detectors are expected to feature a better angu- at the selected site was assessed. lar resolution than that of an ice-based detector. The • Amechanical test-line deployment has validated current Antares demonstrator experiment entails a sci- launching procedures and assessed the Fourier entific and technical research and development project spectrum of accelerations and line movements that has the objective to optimise the performance of during launching, landing and recovery. underwater neutrino detectors. In addition, first observations of cosmic neutrino events are foreseen with • The Main Electro Optical Cable (40 km long), alower-energybound of a few tens of GeV. In view providing electrical power and the optical fibre of the exploratory nature of cosmic neutrino research, links between detector and shore station, has a data sample as unbiased as possible is desirable. At been laid. NIKHEF, we therefore developed the ’All Data to Shore’ concept: timing, amplitude and in some cases wave- form information of the light pulse will be sent to the Responsibilities of NIKHEF in Antares comprise : data-acquisition station on shore (40 km away from the detector) for all photo-multiplier hits. This will allow • Optical–fibre data communication with Dense Wave- maximum flexibility in devising optimal algorithms for length Division Multiplexing (DWDM).

9 • On–shore data router and PC farm (typically 100 of simulated data, equals 0.2◦ and the effective detec- PCs) for data filtering and data archiving. tion volume of the detector has improved with a factor of about 2, as is illustrated in Fig. 2.1. • Run Control and Graphical User Interface. 2.3 Recent developments • Track Reconstruction. Recently, NIKHEF has adopted supplementary tasks in the construction of the Antares detector by taking re- In addition, the NIKHEF–Antares programme leader sponsibility for two key features of the electrical off- coordinates the Readout subproject, comprising Data shore power system – String Power Module (SPM) and Acquisition, trigger, Slow Control and database. local Power Box (PB). DWDM optical fibre communication The SPM provides electrical power (1 kW) to the Local Control Modules and the Optical Modules (OM) of a The counting rate of the 10” photo-multipliers is en- detector line by converting 500 V/AC to 380 V/DC on tirely dominated by beta decay of 40Kintheseawater 6independent outputs, each output feeding one sector and by bursts of bioluminescence. The average count- of a line. The requirements of optimal reliability (design ing rate of about 70 kHz leads to a total data rate goal: 50 years mtbf) and a lifetime of 10 years implies of about 1 GByte/sec. The technology of choice for the use of military-specs components and production transporting the data is dense wavelength division mul- standards. The project has been outsourced to industry. tiplexing. The NIKHEF group has designed a read-out Aprototype has been delivered in December 2001. system based on this modern optical fibre communication technology. A proof of concept of the DWDM Functionality of the Power Box comprises DC/DC con- electronic design has been established in summer 2001. version of the 380 V input voltage to the various DC Special care has been invested to assure the reliabil- voltages that provide power for the LCM– and OM elec- ity of the design by optimising the mean time between tronics. A prototype with a power conversion efficiency failure (mtbf) of components and improving other rel- of better than 85% is being designed by industry in evant design features, such as a minimal temperature collaboration with the NIKHEF Electronics–Technology in the Local Control Module (LCM). The latter feature Department. Series production of Power Boxes is fore- was implemented by a complete redesign of the LCM seen to start in March 2002. cooling system, resulting in a 10◦ reduction of the working temperature. The series production will start April 2002. On-shore data acquisition system 500 New The NIKHEF group is designing the on-shore data pro- 400 cessing system which will consist of a medium sized Old PC farm. A fast algorithm has been developed, in col- 300 laboration with the Centre de Physique des Particules de Marseille (CPPM), that can filter the physics sig- 200 nals from the background at the foreseen maximum Number of events data rate. This data-reduction algorithm will reduce the 100 speed of the data writer to ≤10 MByte/s. It has been shown that with a real time simulation of the sector line, 0 the data processing requirements can be met. A run- 0.01 0.1 110100 control system is being developed that enables remote resolution (deg) operation of the detector, including on-line monitoring and data storage. Figure 2.1: Number of reconstructed Monte-Carlo Track reconstruction events as a function of the angular resolution for two Our contribution to the off-line reconstruction software different track-reconstruction algorithms. The curve la- developments has resulted in a substantial improvement belled “new” corresponds to an algorithm recently de- of the muon reconstruction efficiency and track angular veloped at NIKHEF; the curve labelled “old” is obtained resolution. The angular resolution, obtained with a set with the standard Antares reconstruction software.

10 3TheATLASExperiment

3.1 Introduction information in the second level trigger. This work is conceptually advanced and implementation is about to An important event in 2001 for the ATLAS/D0 group start, in time to be ready when the hardware is com- was the registration of the firstTevatron Run 2 pp¯ missioned. A Nijmegen electronics engineer is spending interaction by the D0 experiment on April 3, 2001. part of his time on implementing the VHDL code for Regarding the ATLAS experiment at CERN, we finished the Field Programmable Gate Arrays that interface the aperiodofintensive preparation for theassembly of first level track trigger to the second level track trigger. muon (MDT) chambers. Since the summer of 2001, Inner tracker magnetic field sensors the MDT chambers are produced at NIKHEF at a speed of about two chambers per week. The Hall probe magnetic field sensor system was al- 3.2 D0 experiment ready succesfully installed in 2000. The system has been used in the final detector configuration to check The Tevatron Run 2 is aimed at collecting an integrated the magnetic field predictions from a theoretical calcu- luminosity of at least 2 fb−1.During most of 2001 lation. The readings of the system are stored in a data the Tevatron collider and the D0 detector were being base, to enable the analysis of the magnetic field, when commissioned. By the end of 2001 both the collider and this is required for the analysis. the experiment seem to have reached a stable mode of Forward proton detectors operation. Engineering support has been given to the design of AFermilab staff member who supervises some of the the roman pot system. The vacuum pots and the po- Dutch students has become a “bijzonder hoogleraar” sitioning mechanism for the castles in which these are at the University of Amsterdam and held his inaugural mounted have been made by NIKHEF Amsterdam. At speech about the D0 detector and its physics in 2001. theend of 2001, ten stations of the Forward proton Three PhD students have returned from a nearly two detectors were installed and commissioning and cali- year stay at Fermilab to the Netherlands. This, together bration has started using colliding beams. with the staff members that joined the D0 collaboration in 2000 and 2001 and actively pursue local computing 3.2.2 D0 software progress at NIKHEF, has caused the groups in the Netherlands Reconstruction software and offline analysis to become important analysis groups within D0. With thearrivalofthe first data, in 2001 there has been 3.2.1D0detector status (NIKHEF-responsibilities) ashiftfrom a concentrated effort in the reconstruction Radiation monitor and beam abort system software to data analyses. One of the NIKHEF PhD students won the prize for finding the first reconstructed This system consists of two parts: beam loss moni- muon in the D0 data. Another nice event found by a tors, argon filled proportional tubes that have been pur- − NIKHEF PhD student is the inclusive Z → µ+µ event chased from the Fermilab beams division and for which candidate shown in Fig. 3.1. Analyses of data and mounting supports were made in Nijmegen; and sili- Monte Carlo studies are being performed for b-quark con diode sensors which are an integral part of the D0 tagging using semi-leptonic decay in muons and using Silicon Microvertex Tracker design. The radiation mon- track impact parameters. The first J/ψ’s have been itoring system has been commissioned and functions as reconstructed using their decay in muon pairs. Recon- expected. Several beam aborts have been triggered by struction of tau-leptons in the data has started, while the system in cases where radiation damage threatened also the analysis of single top quark events and top-pair the detector. A student from the University of Twente decays into all jets has started. At a reduced level the has cross calibrated the different measurement channels group is still contributing to the offline reconstruction in a three month internship at Fermilab. software, notably for muon tracking. Silicon Track Trigger Monte Carlo event production The design of the Silicon Track Trigger has been estab- NIKHEF is the second biggest production center for D0 lished and the system is in production now. A Dutch Monte Carlo events. A 50 node dual processor farm is PhD student is working on using this refined tracking in full operation. Many contributions were made by

11 X-ray scans with the ATLAS tomograph at CERN. The analysis software was written in C++ by a Dutch PhD student. The root mean square of the position deviations from the a-priori fixed grid was found to be about 15 µmfor both chambers, thus amply fulfilling the 20 µmrequirement for this parameter. Moreover the individual small deviations of the wires were found to be very well correlated with the values found with the various RASNIK and planarity laser checks which are part of the quality control and assurance procedures during chamber construction. This shows that handling of the precision mechanics is well under control during the gluing of the tube layers. Several modifications of the jigging tools were made to Figure 3.1: D0 inclusive Z → µ+µ− event candidate. facilitate and speed up the production. The total me- The two muons are the tracks indicated in green ex- chanical assembly time of one complete chamber went tending to the muon spectrometer. The other activity from 20 to approximately 9 working days in the course in the detector stems from the (anti-) proton remnants. of the year. In 2002 we aim to reduce this further to 7 working days per chamber in order to finish the production and start the installation of the chambers in the ATLASexperiment in 2004. the NIKHEF group to the organisation of the Monte Carlo simulation and to the data transfer between the MDT chamber test stand Netherlands and Fermilab. This effort is integrated in With the mechanical aspects of the MDT chamber pro- the more general GRID effort that NIKHEF participates duction under control, we started to work on an MDT in. At the end of 2001 a processor farm at Nijmegen chamber test stand. This stand uses cosmic ray muons University was also started, in first instance with the (triggered by a scintillator counter array) to evaluate aim of doing offline analysis on the D0 data, but with the performance of MDT chambers as a charged parti- the prospect of also producing Monte Carlo events in cle trajectory tracker. The setup at NIKHEF Amster- otherwise empty CPU cycles. dam houses a maximum of five MDT chambers and will 3.3 ATLAS experiment be operational throughout the MDT chamber production period. In addition to MDT chamber studies the 3.3.1 Muon Spectrometer same setup will be used to develop the muon spectrom- MDT chamber construction eter reconstruction and simulation software for ATLAS; to evaluate the performance of the high level data ac- In thesummer of 2001 NIKHEF started the serial pro- quisition electronics and the detector control system. duction of the 96 large muon chambers to be installed Finally, this setup serves as an ideal on site laboratory in the Barrel Outer Layer (BOL) of the ATLAS muon to familiarize physics students and beginning PhD stu- spectrometer. A BOL chamber consists of 432 alu- dents with the many hard- and software related aspects minium drift tubes of approximately 5 m length and of a particle physics experiment. Starting in the spring 30 mm diameter with a tungsten wire held at the tube of 2002 it will be an integral part of the UvA physics centre by precision endplugs. These drift tubes are curriculum. wired using a semi-automatic robot which produces typically 80 drift tubes per day. The rejection rate after 3.3.2 End Cap Toroids stringent quality control tests on wire location, wire The ATLAS End Cap Toroids (ECTs) are an in kind tension, gas leak rate and high voltage characteristics contribution of NIKHEF to the ATLAS collaboration. is about 2%. In 2001 about 5,000 drift tubes were pro- Their basic design was made by the Rutherford Ap- × duced. The drift tubes are glued in 2 3layersoneither pleton Laboratory. Dutch Industry is responsible for side of a support structure, leading to a drift chamber the manufacturing. Contracts for the manufacturing × × dimension of 5 2.1 0.6m.Intotal8chambers were were signed in February 1999. NIKHEF’s supply for produced in 2001. For four of these the mechanical the ECTs consists of three major parts: precision of the wire positions was measured through

12 1. A 1:5 scale model of the vacuum vessels, completed and tested in 1998.

2. Two aluminium vacuum vessels of 10.7 m diameter and 5 m axial length and a weight of 80 ton each. Each vessel houses a cold mass.

3. Two cold masses each consisting of eight superconducting coils of 4×4.5m2 and eight keystone boxes. The keystone boxes are used as reinforce- ment of the whole structure and form a major part of the cold “buﬀer”. The coils are indirectly cooled. The weight of a cold mass is 160 ton.

Vacuum Vessel The two vacuum vessels are made by Schelde Exotech in Vlissingen. Manufacturing started mid 1999. All welding was done by Exotech and the final machining was performed by Machinefabriek Amersfoort in IJssel- stein. The vessels are first fully assembled and vacuum tested at works and then transported in two halves to an assembly hall at CERN. The first vessel was assembled at CERN just before Christmas 2001 (see Fig.3.2). No vacuum leaks were found and within a few days a pressure of 10−3 Pa was achieved. The second vessel is presently being assembled at works and is scheduled to be tested at CERN before Summer 2002, almost in Figure 3.2: The first vacuum vessel assembled at time. CERN. Cold Mass HMA Power Systems in Ridderkerk manufactures the The two silicon wafers in each module were succes- twocold masses. In 2000 the company became part fully aligned to an excellent precision of 1 micrometer. of the Brush Generator division of FKI (UK). The fab- The modules also functioned well electrically. However rication problems encountered by one of the two sup- the circuit board used (known as “K4”) has some ex- pliers of the superconducting conductor have now been cess feedback from its power supplies to the sensitive resolved so the supply of conductor is no longer endan- amplifiers. This problem was investigated at NIKHEF gered. In 2001 the vacuum impregnation of the coils and a solution with extra power-supply filters was found was thoroughly tested. The qualification of both the which worked well for our short modules. However, this vacuum mould and the resin mixing machine gave prob- solution did not cure the problem on modules made lems that have not been solved yet. Proper cleaning of elsewhere which have longer silicon detectors. Instead all material that has to be impregnated is essential for anewcircuit, K5 has been developed by the collab- the bonding. Qualification of the cleaning is close to oration, as well as a back-up solution using a circuit acceptance. The impregnation procedure will be tested adapted from another part of the detector. Both these through the impregnation of the dummy coil, which was solutions work and one will be chosen in February 2002, succesfully produced at the end of 2000. allowing us to proceed to module production in 2003. This will allow the assembly of the 16 aluminium coil Engineering work progressed very well with the comple- formers and the start of the winding. tion of tests on prototypes of carbon fibre support discs. This culminated in the Final Design Review in October 3.3.3 Semi-Conductor Tracker 2001, which was successfully passed. Now the search Early in 2001 we constructed three silicon-detector- is on for a manufacturer to make the 20 discs needed. module prototypes; one of these is shown in figure 3.3. We have also developed a compliant joint to hold the

13 System (ROS) and utilising the ROB hardware developed earlier.

2. Paper and computer modelling of the trigger and DAQ system, including a Monte-Carlo study of event fragment size distributions for the inner detector and of possible lossless data compression algorithms for data from the Transition Radiation Tracker (TRT).

3. The “On-Line Software”, in particular with respect to the information exchange with the DCS and to general support for test software.

4. The software for the ELMB, a dual processor CAN node to beusedforcontroloftheATLAS detectors.

Directly related to these contributions is the development of the MROD, a Read-Out Driver for the muon chambers. The new prototype MROD-1 design was Figure 3.3: Silicon module. completed. This consists of a 9U VME board to which up to 6 chambers can be connected. One board and two associated daughter boards have been produced, discs in the support cylinder. The discs must be held most of the functional testing has been successfully firmly in place without vibrating, but the fixation must completed in 2001. also allow for differences in expansion of the disc and support cylinder, without excessive force. Prototypes In October 2001 NIKHEF has been the host of a work- of the fixing have been made and tested with excellent shop on the DCS, while in November 2001 the annual success. Major progress has been made in developing a trigger/DAQ workshop took place at NIKHEF. gas-tight transport and storage box for the discs. This 3.3.5 Reconstruction & Simulation Software must protect the discs, which when complete will be worthabout 250,000 EUR each. The time-line for the year 2001 for the computing model had the following important issues: migration to object- The Semi-Conductor Tracker (SCT) detectors must be oriented framework, validation oftheGeant4 toolkit kept cold and dry in an inert atmosphere, requiring a and a first order continuity check of the new software flush of nitrogen gas. The group’s experience in wire- (Data Challenge Zero). For the year 2002 the ATLAS chamber gas-systems has allowed us to take on the de- computing challenge includes a “large scale reconstruc- sign of this system, which must keep the pressure in the tion and analysis” (Data Challenge One), a process- enclosures to 1 mbar above atmospheric pressure at all ing farm being able to produce around 10% of ATLAS’ times, despite atmospheric pressure variations of up to needs (including GRID model) and to produce some 100 200 mbar. TB of Monte Carlo data. At ATLAS a control frame- 3.3.4 Trigger, Data-Acquisition & Detector Con- work for simulation issues (“Goofy”) is being developed trol separately from a frame for the digitization, reconstruction and analysis programmes (“Athena”). Both have In 2001 activities on the ATLAS trigger, DAQ and De- their advantages and are currently supported within tector Control (DCS) system were focused on design ATLAS. The simulation control framework “Goofy”, is and implementation work and on studies needed for build on top of the Geant4 simulation toolkit. This preparing the Technical Design Report, to be submit- toolkit, the C++ follow-up of Geant3, is developed at tedatthe end of 2002. NIKHEF contributed in the CERN. The programme was validated last year by sev- following areas: eral ATLAS sub-detector groups to increase thrust in Geant4 simulation so that it can be used for data pro- 1. Studies relevant for the design of the Read-Out duction. The status of Geant4 can be compared to

14 the status of Geant3 just before the turn-on of LEP. “Athena” is a control framework that represents a concrete description of the abstractions or components and how they interact with each other. The architecture underlying Athena is the GAUDI architecture originally developed by LHCb. This architecture has been extended through collaboration with ATLAS. Athena is the sum of this kernel framework, together with ATLAS-specific enhancements. The latter include the event data model and event generator framework. Detector Description NIKHEF plays an important role in the detector description of ATLAS. The description of the detector geometry is isolated from all ‘client’ programmes, i.e. simulation, reconstruction and visualisation packages. To describe the detector geometry, including logical structure, readout tree and a material database. A syntax in XML was developed and adopted by the ATLAS collaboration. The syntax utilises the symmetries as present Figure 3.4: Simulation of a cosmic ray muon traversing in the geometry of the ATLAS detector. By using the the MDT chamber test stand in NIKHEF Amsterdam. XMLindustry standard many utility tools like inspection, validation and visualisation tools are facilitated. The extreme complexity of the ATLAS geometry ne- logical entity in the description corresponds to the de- cessitates the introduction of algorithmic descriptions. tector element (a pixel module or a SCT module side). We have extended the syntax in XML to allow, besides It contains information about its own local geometry, averyexplicit internal geometry description, connec- its global orientation in ATLAS and has a unique logical tion to external algorithms in C++. One can build identifier. The detector element will further be used by these complex, optimised geometries starting from the reconstruction algorithms as starting point for track de- parameters stored in XML, We have created an auto- termination. For the SCT detector a software package matic tool to convert the geometry as described in XML is being written to build the detector elements directly to Geant4 objects. As an example, we show in Fig. 3.4 from the parametric description of the SCT. This code the geometry of the muon chambers in the cosmic ray can easily be extended to the pixel detector. test stand. This geometry is described by XML and automatically converted to Geant4 in order to simulate 3.4 ATLAS detector R&D spin-off the passing of a cosmic muon. 3.4.1 Medipix: Lowering the radiation dose for X- Inner Detector ray imaging We developed the code for the new transient repre- Over 65 thousand of microscopically small X-ray de- sentation of the pixel and SCT event data. The main tectors have been integrated on an area of 2 square improvement with respect to the previous code is, apart centimeters in the Medipix-2 detector, a chip that is from the extensive use of object oriented techniques, to able to count individual photons and convert them into have a description of the data much closer to the data images. The principle of the detector is illustrated in format which will come out of the detector in the fu- Fig. 3.5. ture. Although the code is dedicated to the pixel and In collaboration with the Circuit-Design group of prof. SCT detectors, the overall infra-structure (event con- B. Nauta at the MESA+ Research Institute in Twente, tainers) has been inherited from the common ATLAS of CERN in Geneva, and of the Medical Physics group code. For the pixel and SCT detectors all the neces- of the University Federico II of Naples, the Medipix sary information about the segmentation into diodes of team at NIKHEF has adapted the semiconductor pixel the modules and the connection scheme between these detector technology of the LHC experiments at CERN diodes and the readout electronics are provided. This for X-ray imaging, the main difference being the in- information is interfaced with the XML files. A central clusion in every pixel of a digital counter. The new

15 imaging method is up to 50 times more sensitive than with 65k lead/tin solder balls, in a photolithographic current methods based on scintillators and CCD’s or process called ‘bump-bonding’ by VTT, a company in photographic films. This implies that patients, but also Finland. dentists and other medical staff using X-rays during di- SAF/NIKHEF has designed and built the interface unit, agnostics and therapy, will be exposed to a lower dose based on a Field Programmable Logic Array. This cir- of ionising radiation. cuit does the parallel to serial conversion at speeds up The Medipix-2 detector consists of a sensor chip with to 200 MHz, and the signal level conversions. The Uni- 65k semi conducting sensor diodes, an electronic chip versity of Naples has contributed the software. with 65k amplifiers, comparators, and digital coun- The next goal is to combine eight Medipix-2 chips on ters, and an interface unit connecting the detector to asinglesensormatrix,toobtain a larger imaging area astandard PC. Every pixel constitutes a complete X- of 28 x 56 mm2 and a total of 0.5 million pixels. ray counter, and thanks to the modern deep-submicron technologies, the size of such a pixel has been reduced Industry has shown interest. A contract has been signed to only 55 x 55 µm2.Thedigital to analog convert- with Philips, giving them a license for commercial ap- ers of the chip have been designed by NIKHEF and plication of the chip, the interface and the software. MESA+, while the pixel matrix was done at the micro- This money will be used to further improve the tech- electronics department at CERN. Production of the nology, e.g. to move from current 0.25 to 0.13 micron electronics chip is done by IBM in the United States, technology, allowing still more and still smaller pixels the sensor chip is produced by Canberra Semiconduc- on the chip. Also ESRF in Grenoble has shown interest tors in Belgium. The two chips are soldered together to use our detectors at synchrotron experiments. Activities at NIKHEF in 2001 included the design of 8-bit Digital to Analog converters for the MEDIPIX- 2chipin0.25microntechnology. These circuits are now also used as design blocks in other chips for the ALICE and the LHC−bdetectors. In addition, several different 4-bit pixel-level Analog to Digital Converter designs have been submitted in two Multi Project Wafer runs in 0.25 micron technology, via CERN-MIC. Ten Medipix-1 CMOS readout wafers have been probed at the NIKHEF semi-automatic probe station. In collaboration with our Electronics Technology (ET) department, a 2 by 4 Multi-chip carrier was designed, to carry a tiled array of 8 MEDIPIX-2 chips, allowing an X-ray imager with 28 x 56 mm2 sensitive area. It uses cutting edge high-density interconnect technology, with a nine-layer printed wire board in stacked microvia buildup technology. The board is now in production at aspecial workshop at CERN. Also in collaboration with the ET department, an interface unit was designed and built, to control and readout this multichip board via a standard commercial Dig- ital I/O PCIbus card mounted in a PC. The communication is based on a high bandwidth serial token ring protocol, using Low Voltage Differential Signaling (LVDS). The serialisation, de-serialization and all other func- Figure 3.5: Schematic representation of the Medipix-2 tionalities are performed in a high-speed programmable detector. Incoming quanta of X-ray radiation cause logic chip (Altera FPGA EP20K100EQC240-1X). A se- small electrical pulses in the semiconducting sensor, rial loop speed of 200 Mhz has already been demon- that are then counted in the deep submicron CMOS strated. Production of 25 of these interface units has chip. been outsourced to an external Dutch company. Af-

16 ter testing they will be made available to the members of the MEDIPIX Collaboration, and to our industrial partner. Finally, preparations have been made for the 4th In- ternational Workshop on Radiation Imaging Detectors (IWORID2002), which will be hosted by NIKHEF in September 8-12, 2002. 3.4.2 Diamond Detector Research The use of diamond as a medium for detecting high energetic particles is investigated at NIKHEF in the framework of the RD42 collaboration. Diamond has the advantage over silicon of a better radiation tolerance. However, it suffers from limited charge collection efficiency due to charge traps in the bulk. The material under investigation is made using the CVD process allowing substrates of at least 100 mm diameter. In the report year six recently produced samples were characterised using the test set-up at NIKHEF. The average charge signal of four of them ranged from 8100 to 10000 electrons indicating a charge collection efficiency of 48 to 59%. The charge signal distribution had a Landau shape with a width (FWHM/mip) of 1.05, a value caused by the polycrystalline nature of CVD diamond. These results indicate that the recently produced material has sufficient qualities for use as a tracker in high-energy physics. During an invited stay at the University of Florence the NIKHEF routines forDAQ and analysis were installed and a contribution was given to the improvement of the characterisation set-up. For 2002 a radiation tolerance test for 1 MeV neutrons is planned at Debrecen (Hungary) in collaboration with the University of Florence.

17 Experimental wakeﬁeldsupressor for the LHCB-Vertex Detector. The Wake Field Suppressor is made of two 0.075 mm thin CuBe foils.

18 4B-physics 4.1 Introduction 4.2 HERA-B Field theories constitute the basis of present-day physics. During the past year, much work was accomplished on Three discrete operations are possible symmetries of the hardware of the detector, as well on the analysis the Lagrangian. Two of them, parity P and time re- of the data taken during the commissioning period in versal T ,arespacetime symmetries. The third, a non- summer 2000. spacetime symmetry, concerns charge conjugation de- Trigger Linkboards and Optical Links noted by C,whichoperation interchanges particles and antiparticles. In 1964 it was shown for the first time The Trigger Linkboards (TLink) serialise the TDC- that matter and antimatter behave differently. The information of part of the inner and outer tracker de- undisputed proof was delivered by a delicate experiment tectors and send it at GHz rate via optical fibres to the that revealed a small difference between the decay of First Level Trigger (FLT). Asthisispartofthetrig- neutral kaons and their antiparticles. Since then, for ger that performs tracking on-line, it must be highly nearly forty years, the violation of CP and the violation efficient. The year 2000 run, however, showed that a of time reversal has only been observed in kaon decay. major part of the connections was not working reliably. The kaon data constrain the parameters of the mix- During the shut-down of HERA, since September 2000, ing matrix (CKM matrix) of the Standard Model, but the Linkboards and connections, including the drivers do not constitute a test of it. However, the Standard and receivers, were thoroughly tested, corrected and Model gives precise predictions for a series of CP violat- adjusted. ing effects in the decay of B-mesons. A large number of independent measurements can be carried out in the B The data transmission was tested in order to check for system; thus, it becomes possible to submit the present missing bits and bad solder connections on the TLink. theories to stringent tests. The year 2001 presented a This has been done with a code that reads out the con- milestone in this line of research: thanks to the experi- tent of the Wire Memory (WM) of the Track-Finding ments BaBar at the Stanford Linear Accelerator Center Units TFUs and checks that all data bits are recorded in the U.S.A. and Belle at KEK in Japan the existence correctly. of CP violationintheB-meson system has been firmly Abit-error test was conducted by measuring the bit- established. error rate of the transmission line. By checking for re- peating Bunch-Crossing numbers in the Wire Memory, The LHC proton-proton accelerator at CERN will pro- 8 duce an abundance of B-mesons. Starting in 2006, up to 10 bits per second can be checked. In general, thetest was done for 1200 seconds corresponding to the LHCb experiment, in which NIKHEF participates, −11 will investigate the origin of CP violation and study abit-error rate of 10 .Thesetests were done for whether radically new and different laws of physics will all links in the Trigger, Pattern-recognition and MUON be needed for the description of this phenomenon. With chambers. In January 2002, not more than two prob- aproduction of 1012 bb¯ pairs per year a wide range of lematic links per chamber persist, which corresponds to B decay modes can be studied. In this way it is possible less than 1% of all links. to over-constrain and extract all four parameters of the In order to implement the Inner Tracker into the First CKM matrix even in the presence of new physics. In Level Trigger, the required geometry files were prepared 2001 significant progress was achieved in the prepara- to fill the wire memories in the FLT simulation code. tion of LHCb. The technical designs for both the vertex detector and the large drift chambers have been finished In order to verify that all connections between the TDCs and documented. Both designs have been evaluated by and FLT indeed correspond to the required geometry, the LHCC (a CERN review committee) and brought up and that all data are transmitted correctly, an event-by- for approval to the CERN management. The produc- event comparison between Outer-Tracker hits and Wire tion of both detectors can commence in 2002, allowing Memory has been started. Until now, this was done on atimelystartof the LHCb experiment. astatistical basis only. In order to gather experience in CP-violation physics, J/ψ-production NIKHEF is presently participating in the HERA-B ex- The formation of quarkonium states, and specifically of periment at DESY. J/ψ’s, is at the centre of lively debate for several rea-

19 1 1.1 α this analysis, J/ ψ→ µ+µ-

0.95 this analysis, J/ ψ→ e+e- 1 E866, J/ψ→ µ+µ- 0.9 ψ J/

0.85 α 0.9

0.8 -0.4 -0.2 0 0.2 0.4 0.8 xF

0.7 00.5 x Figure 4.1: Estimated uncertainty (hatched) in α versus F XFeynman for J/ψ-production at Hera-B. Figure 4.2: Two preliminary data points for the factor αJ/ψ (summer 2000 - commissioning data) compared sons. On the one hand, suppression of J/ψ-production to data from the Fermilab experiment E866. in the interaction between energetic heavy ions, charac- J/ψ J/ψ α terised by σpA = σpN A ,isbelieved to be the clearest indication of the formation of a Quark-Gluon Plasma. mass spectrum of electron pairs after several cuts, the On the other hand, the formation process itself is highly most important being the condition that the common interesting, since it yields information on perturbative vertex of the two electron tracks does not coincide with as well as nonperturbative QCD aspects. Since the one of the wire targets of a primary vertex, and that trigger of Hera-B is geared towards the leptonic decay the two-electron vertex is at least 0.5 cm downstream of J/ψ’s, and the target station of Hera-B contains of the target wire. The background has been estimated different materials, a study of the dependence of J/ψ- from detached vertices at the wrong (upstream) side of production on the nuclear mass can be performed with the wire and has been subtracted from the spectrum small systematic uncertainty. Because of its large ac- shown here. An enhancement at the correct J/ψ mass ceptance for both charged and neutral particles, Hera-B is observed. Extraction of the cross section is under offers the unique possibility to study charmonium for- way. mation at negative values of the Feynman scaling variable XF ,tostudy the correlation between the charmo- nia and other particles in the event (co-mover scenarios, double pomeron exchange) and to study the formation → of P-wave χc states via their decay χc J/ψ + γ. 3 2 electron mass Fig. 4.1 shows the estimated accuracy in α for J/ψ- 2.5 production versus XF at Hera-B. The data points represent published values for α from Fermilab experiments and indicate that the acceptance in previous experi- 2 ments does not extend to negative values of XF . Fig. 4.2 compares two preliminary data points of Hera- 1.5 B(runsummer 2000) with the results of the Fermilab experiment E866. 1 B-meson production cross section 0.5 In spite of the very small fraction of interactions that contain B-mesons decaying via B → J/ψ + X, J/ψ → 0 two leptons, and the very limited trigger possibilities in 2 2.5 3 3.5 4 4.5 5 the year 2000, Hera-B succeeded in isolating the first GeV spectrum of B-mesons. For this, use has been made of the different decay lengths of a J/ψ,whichdecays virtu- ally at the spot of production, and of a B-meson, which Figure 4.3: Mass spectrum of detached J/ψ vertices has a typical decay length of 1.1 cm. Fig. 4.3 shows a indicative of B-meson decay (preliminary).

20 4.3 LHCb Outer Tracker An Ar/CF4/CO2 gas mixture will be used as drift gas: the presence of CF takes care of the re- The Research and Development (R&D) carried out by 4 quirement for fastdrift-times,necessary to min- theOuter Tracker group led, in the course of 2001, to imize the overlap of signals from different LHC the production of prototype detector modules, which bunches. were then tested in the pion beam (T7) of the PS accelerator at CERN. The analysis of the test-beam data • Cathode material (See Fig. 4.4) showed that these prototypes attained the desired space resolution (∼200 µm) and efficiency To minimize the effects of the gas contamination (∼97%). due to the decomposition of CF4 molecules, the straw-tube material will be Kapton with a volume From the R&D and the test-beam results a set of base- doping of carbon (Kapton XC-160). line solutions emerged for the technical design of the Outer Tracker, which were summarized in the Techni- • Electrical configuration cal Design Report (TDR). The approval of the Outer In the course of the R&D, we carried out very Tracker TDR by the LHCC has therefore marked an im- detailed studies of the detector electrical con- portant milestone for the project. The principal baseline figuration, that led to the following conclusions: solutions presented in the TDR are: leaving open the end of the anode wire far from the preamplifier will compensate (thanks to the • Detector configuration reflected signal component) the signal attentua- Each station will consist of 4 detector planes tion caused by the high resistance of these long (XUVX), with wires running vertically (X) and wires; an outer winding of aluminum foil (25 µm) under ±5o from the vertical (U and V). will greatly reduce the analog cross-talk between Each plane will consists of basic detector units neighbouring straws; the outer aluminum wind- (’modules’) mounted on aluminum frames, as ing will be contacted to the ground plane at least shown in Fig. 4.5. every 20 cm to prevent oscillatory behaviour. The cross section of a module, containing two • Front-end electronics staggered layers of straw tubes inside a gas-tight For the front-end electronics, we will adopt the box, is shown inFig.4.6. ASDBLR chip (orginally developed for the AT- Each of the two sandwich panels has a 10 mm LAS Transition Radition Tracker), containing 8 thick core material and two 0.1 mm thick carbon- channels of preamplifier, shaper, discriminator fiber composite facings, plus an aluminum foil on and baseline restorer circuitry, implemented in the inner side to ensure electrical shielding and DMILL technology, which offers excellent radia- ground connection. • Gas mixture

Figure 4.4: Eﬃciency and resolution of a test-prototype detector module as a 4function of the operating volt- Figure 4.5: View of the mounting of a station half and age. its subdivision into modules.

21 Figure 4.6: Cross section of a straw tube module. Figure 4.7: Exploded view of an OTR module assembly.

tion hardness and thus allows on-detector mounting. While Kapton XC has been selected as the basic straw- tube material, the details of the production technique • Drift-time measurement electronics will have an inﬂuence on the mechanical properties of The Outer-Tracker Time Information System the straws (See Fig. 4.8). In particular, the number (OTIS) TDC, with a clock-driven architecture es- of windings and the glueing procedure will strongly in- pecially developed for the LHCb Outer Tracker in ﬂuence the mechanical resistance and the gas tight- the ASIC laboratory in Heidelberg, will be the ness of the straws themselves. In collaboration with baseline solution. It will be implemented in a LAMINA Dielectrics Ltd., several test batches of straw radiation-hardness process to allow on-detector mounting.

Preparation of Detector Production and Quality Control Since the approval of the TDR, the focus of our work has shifted from R&D towards production and quality tests. All designs presented in the TDR are translated into detailed technical solutions that can be implemented in the production scheme outlined in the TDR. The construction of an assembly facility, including clean- rooms, suitable to mass production of the longest (∼5m) detector modules is under way at NIKHEF. The key elements for the production of detector modules are the sandwich panels (see Fig. 4.7). Our strict mechanical requirements, combined with the requirement of a minimum material budget, render the production of these panels as standard industrial laminates diﬃcult and expensive. The Cracow Institute, having substantial experience in producing carbon-ﬁber composite structures, has produced in a low-temperature process test panels that have given excellent results and Figure 4.8: View of a straw tube with Kapton XC (in- thus provide a viable solution for this production issue. ner) and aluminum (outer) windings.

22 90000 Ar/CO1 65/35 80000 70000 60000 50000 40000 30000 20000 10000 0 020406080100 120 140 160 x=pos(cm),y=I(pA) at 1700.V for wire 5 Figure 4.9: End-piece block (left) and wire locator (right) Figure 4.10: Current measured in a source scan of a test wire as a function of the source position: the sud- tubes with different combinations of windings and glue- den current drops are due to the presence of the wire ing procedures were produced and tested. Our quality locators. tests showed that a loss of pressure well below 10−7 s−1 per individual straw (thus sufficient to assure the desired gas tightness) can be attained with double Kapton 4.4 LHCb Vertex detector XC windings. The required performance of the LHCb Vertex Loca- At the end of each straw tube, wire-support elements tor (VELO) demands positioning of the sensitive area and gas-distribution blocks are necessary. These two of the detectors as close as possible to the beams and functionalities have been combined in a single ’end- with a minimum amount of material in the detector ac- piece’. Additionally, due to their length, wires have ceptance. This is best accomplished by operating the to be supported at intermediate positions by so called silicon sensors in vacuum. However, the need for shield- ’wire locators’. The desing solutions offered by the ing against RF pickup from the LHC beams, and the TDR have been translated into elements suitable for need to protect the LHC vacuum from outgasing of the industrial series production, shown in Fig. 4.9. detector modules, requires a protection to be placed Essential tests of the quality of the detector modules around the detector modules. Furthermore, during in- produced include the accurate determination of the wire jection, the aperture required by the LHC machine in- tensions and of the wire positions. For the wire-tension creases, necessitating the retraction of the two detector measurement, we designed and built a device to deter- halves by 3 cm. Finally, to allow for a replacement of mine the main eigenmode of awirevibratinginamag- the sensors in case of radiation damage, access has to netic field with an accuracy of approximately 0.5 Hz. be rather simple. Asaconsequence, integration into the LHC machine is a central issue in the design of the For the measurement of the wire positions, we devel- VELO. oped a method based on scanning modules with a 90Sr source and recording the cathode current as a function Acompletesystemdesignwas carried out. This in- of the source position (See Fig. 4.10). A dedicated cur- cludes a design of the vacuum vessel, motion and posi- rent meter was built, with a precision of 100 pA, which tioning mechanics, thin-walled structures for RF screen- allows current determination with an accuracy of less ing, systems for cooling, vacuum, monitoring and con- than 1% at low currents, and thus an accurate deter- trol. The VELO vacuum vessel is a 1 m diameter stain- mination (±100 µm) of the position of the wire with less steel vessel of about 1.8m length which is evac- respect to the cathode straw. uated by two powerful ion pumps (combined with Ti- sublimation pumps). The vacuum vessel and associ- This experimental apparatus will also allow the deter- ated vacuum pumps rest on a concrete stand. Finite mination of the I-V characteristic curve of the detector element analysis (FEA) was performed for the vessel modules. and other components (exit window, cooling capillaries, thin-walled detector encapsulation). Extensive prototyping was carried out on critical items, such as the

23 Figure 4.11: 3D-view of the vacuum vessel of the vertex detector. The silicon detectors are placed in a secondary vacuum vessel. For illustrative reasons part of this secondary vacuum vessel has been removed from the front box. Each detector halve is connected to the tank through a large rectangular bellow. During injection the two secondary vacuum vessels will be moved apart.

Figure 4.12: Sample of a 0.25 mm thick encapsulated thin-walled structures, vacuum protection devices, large aluminium foil. rectangular bellows and the cooling system. The new design allows baking out of the primary vacuum surfaces and provides easy access to the silicon sensors. Further, this thin-walled structure must allow for a small overlap between the silicon sensors of the two A3D-viewofthemechanical design of the VELO is opposite halves, implying the use of a complex corru- shown in Fig. 4.11. Large rectangular bellows allow gated structure, and it must accommodate the motion precise movement (in the transverse directions) of the of the detector halves. The fabrication of such com- detectors during data taking as well as complete retrac- plex thin-walled encapsulations is delicate and time- tion of the detector elements prior to filling and dump- consuming. An extensive prototyping programme is on- ing the beam. These large rectangular bellows decouple going, in which various techniques are being studied to the complete VELO detector system from the primary realise the desired shape. Fig. 4.12 shows the current vacuum vessel. The detector halves are attached to a status of these developments. The corrugated foil was frame which can be moved in the two transverse direc- manufactured from a 0.25 mm aluminium-magnesium tions relative to the concrete stand. All motors, bear- alloy AlMg3. ings, gear boxes and chains of the positioning system are outside the vacuum. Coupling to the frame is done The large rectangular bellows (36 cm width × 126 cm via bellows. length) separating the two vacua must accommodate the 30 mm displacement in the horizontal plane (com- The secondary vacuum container represents one of the pression of the bellows) as well as for a ±6mmlateral most critical parts of the VELO structure. The con- displacement in the vertical plane. For the latter rea- tainer must be radiation resistant and act as a wake- son, a pair of bellows separated by a flat section is used field suppressor (electrical properties). In addition, the (see Fig. 4.13). container provides a separation between primary and secondary vacuum (ultra-high vacuum compatibility). These bellows do not need to sustain a differential pres- The container walls located within the LHCb accep- sure of 1 bar, hence a dedicated production method was tance must be manufactured from low-mass material. developed that starts from preformed 0.15 mm thick

24 Figure 4.13: The rectangular bellow.

stainless steel sheets: in a first step the sheets are spot- welded around the edges with a Nickel-alloy (brazing) foil pinched between the two surfaces; in a second step, the Nickel-alloy foil is molten in a vacuum oven. This results in a smooth solder joint. Beam bunches passing through the VELO structures will generate wake fields as a consequence of the geometrical changes and/or of the finite resistivity of the Figure 4.14: The full size mock-up of the vertex vessel wall materials. The generated wake fields can affect for RF tests. both the VELO system (RF pick-up, heat dissipation) and LHC beams (instabilities). Hence, the design must take into account minimisation of heat dissipation, of the coupling impedance, and of the electro-magnetic Two kinds of safety valves are used to protect the thin fields inside the detector housing. The aluminium en- separation foil (detector housing) from an irreversible velope of the silicon stations must be electrically con- deformation, or rupture, in case of a pressure increase nected to the exit window to guarantee appropriate on either side of the foil. A differential pressure switch wake-field suppression and to prevent possible spark- is used to open an electrically activated valve when- ing in this transition region. This constitutes a deli- ever the pressure difference between the primary and cate design issue. The segmented half tapers of these secondary vacua rises above a value 1mbar. If the wake-field suppressors are fabricated from 70 µmthick pressure difference exceeds the value 5mbar, then corrugated copper-beryllium strips. The corrugations agravity-controlled valve opens under the direct effect are needed to allow for mechanical motion of the de- of the pressure independently of any electrical power tector housings relative to the vacuum vessel and exit or pressurised air supply. The principle of this valve window. The performance of the system has been mea- consists essentially of a light aluminium disc resting on sured in a one-to-one scale model of the VELO, shown the end of a tube under the action of gravity. In case in Fig. 4.14. Realistic wake-field suppressors and detec- of an increase of pressure in one of the vacuum sector encapsulations are implemented in this vessel. Sev- tions, the disc moves up directly under the effect of the eral loop antennas are used to monitor the components pressure difference and equalises the pressures in the of the (oscillating) magnetic fields tangent to the wall twovolumes. To reduce the residual valve conductance surface. Measurements of the resonant modes and cou- between the two vacua in normal operation, the valve pling impedance of the mock-up have been performed can be pumped differentially by an auxiliary pump. The by using network analysers. purpose of these safety valves is to maintain the pres-

25 0 tions. The capillaries and ﬂow restrictions are vacuum- [mV] brazed to a manifold. The connection to the detector -20 modules is achieved via an aluminium coupler and a -40 soft metal indium joint. A carbon-ﬁbre substrate provides a mechanical and thermal link to the sensors. The -60 temperature of the coolant in the capillaries is set by

-80 controlling the pressure on the return line (typically 15 bar). In this way, a temperature in the range of - -100 25 to +10 ◦Ccanbemaintained with a total cooling capacity of about 2.5kW (≈ 50 W per cooling capil- -120 lary). 120 140 160 180 200[ns] 220 Arisk analysis was carried out for the VELO to first identify critical parts of the system and their possi- Figure 4.15: Pulse shape measured with the BEE- ble failure scenarios, then to estimate the associated TLE1.1 chip at the X7 test beam of CERN. The values damage (essentially, the downtime for LHC) and finally found for the rise time and overspill amount to 20 ns to define a number of requirements (tests and precau- and 19%, respectively. tions) to be fulfilled in order to bring the system to a level of acceptability compatible with LHC standards. The main conclusion from the risk analysis is that, even in the worst scenario (rupturing of the exit window or sure difference below 17 mbar, the valueabovewhich LHCb beam pipe), the downtime for LHC is not ex- the thin-walled detector housing is expected to deform pected to exceed two weeks. irreversibly. At this pressure, the largest (permanent) displacement on the encapsulation has been calculated An important highlight this year was the submission to be about 0.3 mm. The actual rupture pressure of the of the Technical Design Report for the Vertex Loca- encapsulation is expected to be several hundred mbar. torVELO on May 31, 2001. The TDR has been approved by the CERNResearch Board in its meeting of The complete vacuum system will be controlled by a November 15. In view of the discussions on a reduction PLC unit backed with an uninterruptable power sup- in the material budget (’LHCb-light’) the Board made ply and interfaced to the LHC and LHCb Supervisory the restriction that any change in this design have to be Control and Data-Acquisition (SCADA) systems (via communicated to the LHCC and approved before con- e.g. ethernet). In addition to this software interface, struction commences. Finally a mini-preview meeting hard-wired interlocks between LHC and LHCb will be took place on December 4 at CERN where the status implemented, for example for operation of the sector of the mechanical issues (RF-foil, bellows and vacuum) valves. and RF-issues were discussed. Preliminary studies have shown that electron cloud 4.5 LHCb front-end chip build-up may occur when the VELO is in the open position. The effects on the gas pressure may be tolerable The development of a radiation-hard front-end chip in due to the large pumping speed. However, the emit- 0.25 µmCMOStechnology for the vertex detector of tance increase due to electron space charge has yet to LHCb is in full progress. In a collaboration between the be assessed. A coating with low secondary electron ASIC-lab in Heidelberg, Oxford University and NIKHEF yield on the detector encapsulation might be necessary. an improved design of a 128 channel 40 MHz chip has been submitted. Two of these BEETLE1.1 chips Cooling of the detector modules is required since the have been bonded to a 300 µmVELOprototypePhi- sensors are operated in a high radiation environment. detector. This configuration has been implemented in a This is achieved by using a mixed-phase CO2 cooling setup that subsequently was used for performance tests system. Besides being an adequate coolant for appli- at the X7 test beam of CERN. Data have been collected cations in high radiation environments, CO2 exhibits in coincidence with the VELO beam telescope and in excellent cooling properties. stand-alone mode. Preliminary pulse shape results are

In the proposed cooling circuit, CO2 is supplied as a liq- shown inFig.4.15. uid and expanded into a number of stainless steel cap- The values found for the rise time and overspill are illaries (one line per detector module) via ﬂow restric-

26 DAQ L0

PileUp Veto System Host (Vertex Finder Boards) T1 T2 T3 T4 T5 T6 T7 T8 T9

3m 1000 LVDS ODE HV&LV Exp. VELO Power Control Serialtoparallel Supply Optical Connection 70m 95 opt. fibers Optical Connection Paralleltoserial ECS Slave 10m 1000 LVDS Crate Repeater (+ rad. hard LVDS drivers)

2*4

Hybrid+PitchAdaptor

Figure 4.17: Asimulated B → π+π− event in the Figure 4.16: Schematic overview of the Pile-Up VETO LHCb detector. The curves are the particle trajectories, system. the crosses (‘x’)representthetrackingdetector hits. within LHCB specs. In the mean time new shaper The Pile-Up VETO system is either part of the VELO and pre-amplifier circuits, featuring better character- partition or a partition on its own. It is envisaged to istics from the point of view of saturation, have been use as much as possible standard components of the designed, submitted and measured in the lab. VELO or of the central DAQ system. An ODE Digi- tizer board will be used for the BEETLE output, either The technology used for the design of the chip promises in selectable binary or analog readout mode. The data excellent radiation hardness thanks to special layout to be included in the LHCb data stream flow via the L1 techniques, like enclosed transistors and guard rings. Buffer. Network Processor modules combine the data. Irradiation tests performed on BEETLE1.1 chips did For the Pile-Up VETO system output a dedicated FIFO not show any significant performance degradation up will be provided on the Output Board. The use of the to a total dose of 300 kGy (SiO ), which is equivalent 2 system as luminosity monitor requires an additional out- to 15 years of LHCb running. put as well. The design for the Pile-Up VETO hybrid 4.6 L0 Pile Up Veto System closely follows that of the VELO system. A prototype of the VELO BEETLE hybrid is being designed. It will be In Fig. 4.16 an overview is given of the system. The used in tests for the Pile-Up VETO system. Compared digital signals from the comparators of 16 BEETLE to the VELO system the number of signal paths of the chips on the hybrid are amplified in the Repeater Sta- VETO hybrid is significantly higher because of the ad- tion on the vertex tank (if necessary) and led to an ditional LVDS signal pairs from the comparators. The LVDS-bus-to-Optical-Transceiver Station. Behind the additional connections add complexity to the design. shielding wall the receiver ends of the optical links are located. There, the serialised data will be fanned out The output lines of the Beetle chip are LVDS conform. again. The other output paths of the BEETLE and Perhaps no Repeater Station modules are needed for ECS connections are as described in the VELO TDR in transmitting the digital output, provided the optical 2001. The decision to locate the processor part behind transmission boards can be placed nearby in a more or the shielding wall is governed by the fear for radiation less radiation free environment (estimated rate at 10 m: effects (dose effects, SEUs and SELs) that could occur < 1Gy/y). Otherwise the Repeater Station will house when the system would be located near the vertex tank. modules with radiation hard LVDS drivers (estimated

27 100 100 18 100 99 16 Efficiency 98 14 95 95 97 12 96 10 95 90 90 8 94 6 93 Wrong match fraction (%) match Wrong 85 efficiency(%) Following 85 92 4 Seeding efficiency (%) Seeding efficiency Wrong match fraction 91 2 80 80 90 0 020406080100020406080100051015 20 25 30 35 40 Momentum (GeV)

Figure 4.18: Efficiency versus particle momentum for track seeding (left plot), track following (centre plot) and track matching (right plot). rate: ∼200 Gy/y) to bridge additional distance. Since • Link the measurements in the vertex detector using LVDS for distances over 70 m is not feasible at a with the calorimeters and the muon detector. rate of 80 MHz, optical transmission has been chosen as the baseline solution for transporting the signals to An example of a B → ππ event is shown in Fig. 4.17. the VETO-system. For the L0-Mu trigger prototypes In addition to the B decay particles, on average hun- tests of such a system have been performed. dred background trajectories are observed in the event. The track reconstruction program aims to reconstruct The heart of VETO system is formed by the Vertex all trajectories thattraverse the full spectrometer. With Finder Boards. In total 5 Vertex Finder Boards are the above tasks in mind the layout of the LHCbtracking planned to be used. Four of them handle subsequent detector systems is being optimised for optimal perfor- events. The fifth one is a spare processor board that can mance. The NIKHEF group plays a leading role in the be used for checking the results of the others, provided track reconstruction as well as in the detector optimi- that the data can be routed into it. Algorithms for sation studies. different configurations will be pre-programmed. For a prototype Vertex Finder VME-board the algorithm has Pattern Recognition been translated in VHDL and translated into code for The layout of the tracking system is optimised for up- 3largeXILINXFPGA’s. The prototype board will be stream tracking, where one searches for track segments tested with test patterns. in stations farthest away from the interaction point and 4.7 Track Reconstruction traces particle trajectories backwards through the magnet towards the vertex region. More specific, the pat- The main tracking system, consisting of a series of tern recognition task of assigning series of detector hits stations with Inner Tracker and Outer Tracker com- to particle trajectories is executed in three consecutive ponents, must perform the following tasks: steps:

• Find charged particle tracks in the region between 1. Search of track segments in the downstream seed- the vertex detector and the calorimeters and mea- ing stations T6 - T9, located in a low-field region. sure the particle momenta. The momentum pre- 2. Track propagation through the dipole magnetic cision is an important ingredient of the mass res- field towards the vertex detector. At each station olution of the reconstructed B-mesons. track continuations are searched making use of a Kalman filter procedure. • Provide precise measurements of the direction of track segments in the two RICH detectors, to be 3. Matching of tracks of the main tracker with in- used as input to the particle-identification algo- dependently found track segments in the vertex rithms detector.

28 σ 8 σ 50 =10.7 MeV 50 =21.8 MeV 7 40 6 40

5 30 30 4 p/p (per mille) δ 3 20 20

2 10 10 1

0 0 0 020406080100 120 140 160 180 200 5.2 5.4 5.3 5.35 5.4 5.45

p (GeV) m 0(GeV) B

Figure 4.19: left: Reconstructed momentum resolution as a function of track momentum, center: Mass resolution of reconstructed B → ππ events, right: Mass resolution of reconstructed B → Ds Kevents.

The efficiency of each of these algorithms is shown in ceptance of the experiment. The effects of material Fig. 4.18. Combining the three efficiencies the average areevent losses due to either hadronic interactions of efficiency for a track in the event is 90%, the efficiency final-state particles (pions, kaons, governed by the infor a typical B-decay track is 95%. teraction length λI )orbyelectromagnetic interactions (electrons, photons, governed by the radiation length Momentum Fit and Mass Resolution X0). In addition, dead material leads to secondary par- The found tracks are fitted withaKalmanfitprocedure ticle tracks and multiple scattering, which distort the that takes into account kinks in the trajectories due measurement of the B decay tracks. to multiple scattering in the detector materials. The The following results in the optimisation have been ob- resolution of the reconstructed momentum is shown in 2 × tained: Fig. 4.19. It is parametrised by: δp/p = Ams +(Bres 2 −3 p) with Ams = 3.8 × 10 ,(themultiple scattering −5 • Modification of the beam-pipe design from an term) and Bres = 3.6 × 10 (the resolution term). aluminium based pipe to a beryllium-aluminium The momentum resolution is of crucial importance for alloy based design, with less flanges, reduces the the mass resolution of reconstructed B and D mesons. number of hits in the tracking detectors by a fac- The expected mass resolutions of the reconstructed B- tor of two. meson, in the case of a high multiplicity (B → π+π−) • and a low multiplicity (B → Ds K)benchmark decay are The presence of a trackingstation just down- 21.8 MeV and 10.7 MeV, respectively (see Fig. 4.19). stream of the vertex detector is not crucial for the pattern recognition task of connecting tracks Detector Optimisation in the VELO with tracks in the main tracker. The technical design of most LHCb subdetectors is fin- • The presence of a tracking station at the center ished and presented in the corresponding TDR doc- of the LHCb dipole magnet, where background uments. However, the layout of LHCb is currently conditions are severe, is not crucial for the pattern subjected to final optimisation studies. These studies recognition task of track propagation. serve to reach an optimal physics performance using detectors as designed in the subdetector TDR reports. • The presence of a trackingstation just down- NIKHEF plays a prominent role in these final design stream of RICH-2 is not crucial for the efficiency studies. and mis-tag rate of particle identification. The main aspect in these optimisation studies is to minimise the amount of detector material in the ac- Additional optimisation studies are ongoing that aim to further reduce the amount of material in LHCb, without

29 Figure 4.20: left: Baseline LHCb detector design, right: ’LHCb-light’ design. compromising the performance of the experiment. The • Measurement of the unitarity angle γ using the → ∓ ± following subjects are presently being investigated: decay Bs Ds K .Contrarytothe previous channel, in this decay each charge configuration • Use of lighter materials and thinner detectors can of the final state can be reached by both flavour reduce the integrated amount of material in the B-mesons, allowing for CP violation to occur. VELO and RICH-1 detector from 0.33 X0 to 0.19 The reconstruction of this channel is similar to X0. the previous channel, the main experimental challenge is the suppression of backgrounds. • Removal of the tracking stations just downstream of the VELO (T1) and in the magnet region (T3- • Looking for CP violation caused by physics be- → T6) can reduce the amount of material in the yond the standard model with the decay Bs CP tracking system from 0.27 X0 to 0.12 X0 without J/ψφ.TheStandard Model predicts no losses in efficiency for tracks that traverse the asymmetry, so any observed CP violation in this complete spectrometer. decay indicates the existence of physics beyond the Standard Model. A particularly interesting The layout of the proposed LHCb light detector is com- aspect of the decay is that the final state can be CP pared to baseline geometry in Fig. 4.20. produced by decays of the eigenstates of the Bs meson: Bheavy and Blight .Anangular analysis 4.8 LHCb Physics Performance of the final-state particles also allows a precise measurement of the difference of the decay rate In the physics performance studies NIKHEF focused on of the Bheavy and Blight mesons. the decays of the Bs meson. One of the main challenges of physics with the B meson is to resolve the oscillation s 4.9 Grid Activities frequency of the Bs - B¯s oscillations, for which the lower −1 limit currently is ∆ms > 14 ps .Theexpected decay- Computer ‘Grids’ consist of many machines, perhaps time resolution for reconstructed Bs mesons in LHCb is distributed over a large geographical area, that can col- 3% (see Fig. 4.21). laborate on task execution and/or data storage and The topics studied by NIKHEF are: distribution. The LHC collaborations at CERN plan to use Grid computing to supply the computing resources needed for analysis of the LHC data. About • Measurement of the B oscillation frequency, us- s five petabytes per year of LHC data are expected to be ing a flavour-specific decay channel, i.e. the de- stored, and the total CERN-related analysis effort will cay determines the flavour of the B mesons s require on the order of 50,000 high-end PCs in 2007. at decay. The most promising decay-channel is → ∓ ± Bs Ds π .Current studies indicate a sensi- The LHCb group at NIKHEF has begun preparations −1 tivity up to ∆ms = 60 ps . for the use of DataGrid in its computing efforts. A

30 cluster of ten machines (each with two GHz-class processors) has been installed on the Grid segment of the NIKHEF network. The LHCb simulation framework has been installed, along with the PBS job manager and a web interface to the job-submission program. This cluster is participating in Monte-Carlo production, directed remotely from CERN. When the DataGrid software has been fully installed on the current DataGrid cluster, we plan to add the ten-node LHCb cluster as Grid computational ‘worker nodes’. At this point, the Grid cluster will become available for the collaboration.

→ 140 Bs Ds K

120

100

0 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 Bs time resolution (fs)

Figure 4.21: Reconstructed decay time resolution for simulated Bs → Ds Kevents.Thetimeresolution is 40 fs, corresponding to 3% of the Bs lifetime.

31 First full length 15 metres prototype high ﬁeld superconducting magnet for the Large Hadron Collider (LHC).

32 5CHORUS

The CHORUS experiment at CERN (WA95) has been designed to discover or exclude νµ ↔ ντ oscillations 1.5 mm with high sensitivity in the parameter region of small −3 2 2 mixing (< 10 )and‘large’∆m (> 10 eV ). Data ν 0 were taken during 5 years, from 1994–1998. NIKHEF D 1.5 mm participates in the CHORUS collaboration since 1992.

The characteristic of the CHORUS detector is that – 6.3 mm (8 plates) apart from electronic tracking– it allows high-precision tracking in the massive nuclear emulsion [1] used as neutrino target. This ‘hybrid’ detection provides a pow- Figure 5.1: The NETSCAN [1] volume with a sketch erful method to find unambiguous signatures for sec- (not to scale) of D0 decay. The ellipses represent track → ondary vertices, not only for ντ τ charged-current segments in 100 µmemulsion layers in which automatic ↔ (CC) interactions for the νµ ντ oscillation search [2], scanning is performed. but also for νµ CC interactions producing short-lived charmed hadrons with track lengths of order 100 µm. outer emulsion sheets has been recently completed and In the emulsion target, chargedparticles produce –after scanning inner (‘bulk’) emulsion sheets is being started. development– silver grains with an average size of 1 µm Last year at NIKHEF a pioneering physics study [3] has and a density of 300 per mm. A τ-lepton or charmed been completed, based on 132 charm production –with hadron can be recognized by the topology of the decay muon decay– events. From this sample the ratio of into charged particles. In parallel with the oscillation neutral-to-charged charm production has been deter- search this latter possibility has opened up top-of-the- mined as a function of neutrino energy. In the mean line charm-physics studies. time a sample of already 283 neutral charm D0 events Upon any event trigger in the electronic detector, kine- with different decay topologies has been collected and matic measurements are carried out using the muon and analysed [4]. The D0 production cross section as a the hadron spectrometer, and the 118 t compensating fraction of the total CC cross section as a function of lead ‘spaghetti’ calorimeter. Precise positions and di- the neutrino energy is shown in Fig. 5.2 together with rections of trajectories are deduced from fibre tracker results from an earlier emulsion experiment E531 at planes and special emulsion sheets. For events of in- Fermilab (USA). terest these trajectories are followed backward in the After a CC charm-production study based on di-muon analysis, pointing –with increasing accuracy– the way events from neutrino interactions in the (lead) calorime- towards the corresponding neutrino interaction vertices ter, an analysis of the same data provided the obser- inside the emulsion target. Using automatic scanning vation of weak neutral-current neutrino production of techniques first developed in Nagoya (Japan) and origi- J/Ψ’s [5]. nally mostly hardware controlled, the vertex and emerging tracks are then located with µmprecision. Up to now only massive counter experiments could provide high statistics measurements in the field of charm After years of hardware and software developments physics, while emulsion experiments had the advantage to speed-up and to increase efficiency of the auto- of very low background but the statistics that could be mated track and vertex finding a powerful method reached was limited by the scanning load required. (NETSCAN, see Fig. 5.1) has been developed, which allows essentially full reconstruction of events for which The development of NETSCAN has opened to CHO- the vertex has been located. The emulsion scanning, RUS the possibility to become the first high-statistics still to a major extent being performed in Japan, is sup- emulsion experiment in charm physics thanks to the plemented by essential contributions from several Eu- fact that the full decay-vertex topology can be automat- ropean laboratories. CERN and NIKHEF together op- ically reconstructed for a very large number of events erate an automatic scanning facility (three microscope in a relatively short time. systems with mega-pixel digital cameras) that is fully software controlled. A camera (resolution) upgrade of At themoment about 130,000 events have been anal- the earliest built system is in progress. Scanning of four ysed with NETSCAN. High purity selections were developed to isolate charm events, and a sample of about

33 0.06 were selected for the analysis. After cuts the data sam-

(CC) ple comprises about 1.1M ν-events and 230K ν¯-events. σ

)/ Using a fast dedicated Monte-Carlo simulation correc-

0 0.05 tions for acceptance and experimental resolution are (D

σ applied. The underlying cross-section model is based 0.04 on the GRV94LO [6] parton distributions with modifications to allow for a non-zero longitudinal cross section and nuclear effects. A phenomenological correction im- 0.03 proves the description of the data at low Q2.Some final checks and minor improvements on the analysis 0.02 are in progress to prepare the data for publication. Simultaneous measurementsonfourtargets of widely 0.01 different nuclear composition (polyethylene, marble, iron and lead) to measure ratios of neutrino-nucleus total cross sections for different nuclear targets have been 0 020406080100 120 140 analysed in detail. Some systematic studies are under- Eν (GeV) way to prepare also these data for publication.

Figure 5.2: The CHORUS results for the measured ra- References tio of D0 versus total CC cross section as a function of the neutrino energy, shown as solid crosses and com- [1] S. Aoki et al.,Nucl.Instr.Meth.A473 (2001) 192. pared with those of the E351 experiment (dashed). The curve is based on the slow rescaling model fitted to [2] E. Eskut et al.,Phys.Lett. B497 (2001) 8. NOMAD charm data scaled by the measured (by CHO- RUS) D0/(total charm) ratio. [3] O. Melzer, PhD Thesis, University of Amsterdam, 2001. [4] A. Kayis-Topaksu et al.,Phys.Lett. B527 (2002) 1000 events was manually checked in order to confirm 173. the presence of a charmed particle and to refine the measurement of the parameters of tracks and vertices. [5] E. Eskut et al.,Phys.Lett. B503 (2001) 1. This sample was used for the D0 production study [4] [6] M. Gluck et al.,Z.Phys.C67 (1995) 433. and for a first attempt to determine the production fractions of charged charmed hadrons [7]. [7] F.R. Spada, PhD-thesis University ‘La Sapienza’, Rome, 2002. Many other studies are in progress which aim to determine e.g. the charm production by ν¯µ (from the [8] B.L.F. van de Vyver, PhD-thesis in preparation. antineutrino component of the beam), the charm production via mechanisms other than deep inelastic interactions and Λc production. Recently, a measurement of the total branching fraction of charm into muon has been completed without the need of a manual check [8]. Ahighstatistics data sample with the CHORUS calorimeter as active target was obtained during a dedicated runin1998 after the emulsion data taking was ter- minated. The analysis of these data provided a measurement of neutrino-induced deep-inelastic differen- 2 tial cross-sections on lead, from which F2(x, Q ) and 2 xF3(x, Q ) structure functions can be extracted with a precision comparable to earlier results for iron targets. Neutrinos with an energy between 10 and 200 GeV

34 6HeavyIonPhysics ) 6.1 Introduction -2 WA98 10 (GeV The heavy ion group at NIKHEF participates in the 3 PRELIMINARY

/dp Invariant mass analysis current CERN heavy ion programme. The NIKHEF γ

N 1

3 Inclusive photon analysis contribution to the data analysis of the WA98 experi- E d ment, publishing its ﬁnal conclusions, is described be- Ev -1 10 low. Both the NA57 experiment and the NA49 ex- 1/N

-2 periment are considering additional data taking during 10 the next two years to further investigate the tantalising

-3 hints of the production of a quark-gluon plasma seen 10 in the SPS experiments. -4 10 In addition to the analysis of the SPS data, NIKHEF 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 contributes strongly to the preparation of the ALICE Transverse momentum (GeV/c) experiment. The NIKHEF group concentrates on the design and construction of the ALICE silicon tracker. Figure 6.1: Invariant direct photon yield as observed This work is now in transition between the design phase in central 158 AGeV Pb+Pb collisions by the WA98 and the production phase. experiment. 6.2 Direct photons in WA98 To investigate Quark-Gluon plasma (QGP) formation in a direct way, one needs penetrating probes which reflect the hot early stage of the interaction. currently in progress. Application of this method on the WA98 lead-lead data reveals indeed a possible di- The thermal radiation of a deconfined system is a rect photon signal due to thermal radiation as shown source of direct photons, i.e. photons not originat- in Fig. 6.1. ing from hadron decays. Direct photons are thought to provide an excellent means for studying the state Theoretical models [4, 5] indicate that the temperature of nuclear matter at the various stages of the interac- of the system that is created, determines the shape tion, since photons decouple from the nuclear system of the direct photon spectrum, whereas the absolute immediately after their production and are essentially photon yield reflects the space-time evolution of the uninfluenced by the hadronisation process. radiating system. Consequently, observations of direct photon spectra in the thermal regime are expected to Within WA98 [1] the background problem of the hadronic reveal the temperature profile and space-time history of decay photons has been overcome by reconstruction of the interaction process. the parent π0 and η mesons by means of a two-photon invariant mass analysis. The thus obtained π0 and η The data of WA98 can be compared with theoretical momentum spectra provide the basis for a prediction of calculations based on various values for the tempera- the hadronic decay photon spectrum. This calculated tures corresponding to the start of the QGP phase (T0), spectrum is then subtracted from the actually observed the phase transition (Tc ) and the hadronic freeze-out photon spectrum. WA98 showed [2] that indeed a di- (Tf )[6,7]. rect photon signal is present in the data. However, due In Fig. 6.2 the invariant yield of Fig. 6.1 is shown as a to the limitations imposed by the reconstruction of the function of the photon energy in the cms of the nucleus- parent mesons, only the relatively high p⊥ region could nucleus collision, together with the calculated yield for be investigated with sufficient accuracy. Since in this the values T = 300 MeV, T = 180 MeV and T = region direct photons from hard initial scattering pro- 0 c f 100 MeV. cesses are expected to dominate, no conclusion can be drawn concerning direct photons originating from ther- An overal good agreement of the calculated yields with mal radiation. the data is observed. It should be noted that the various temperatures in the model have not been obtained from In order to investigate the thermal regime, an alterna- minimisation procedures, but have been ’eye-fitted’ and tive analysis based on inclusive photon spectra [3] is put in by hand. However, these values provide agree-

35 100 Pb-Pb 40 AGeV (NA57) 160 AGeV (WA97) T = 300 MeV 0 Λ/Λ¯ 0.023 ± 0.001 0.133 ± 0.007 10 Ξ/Ξ¯ 0.080 ± 0.025 0.249 ± 0.019 p-Be 40 AGeV (NA57) 160 AGeV (WA97) 1 ¯ 3 Λ/Λ 0.059 ± 0.007 0.332 ± 0.008

/dp ¯ γ Ξ/Ξ — 0.45 ± 0.07 N 3 qgp E d 0.1 Table 6.1: Particle anti-particle ratios for the Λ and Ξ.Thevaluesat 40 AGeV are measured by NA57, the hadron gas values at 160 AGeV by WA97. 0.01 sum mixed 0.001 asensitivesignature for the existence of a QGP phase 0 0.5 1 1.5 2 2.5 [9]. 2) E (GeV/c γ In order to study the evolution of strangeness enhancement as a function of the beam energy and as a function of the centrality of the collision, NA57 has mea- Figure 6.2: Data with calculated thermal yields (curves) sured strangeness production at both 40 AGeV and within the framework of a hydrodynamical evolution 158 AGeV. In the most central events the number model [6, 7]. of nucleons undergoing at least one primary inelastic collision (the wounded nucleons) is large. For the more peripheral events the number of wounded nucleons and therefore the size of the produced system is ment with the data. Furthermore, it was observed that much smaller. The number of charged particles de- the dependence on T was only very weak. f tected at mid-rapidity can be related to the number Based onananalysisas the one described above, one of wounded nucleons by the Glauber model [10]. The can make a link between the observations in heavy ion NA57 experiment can detect collisions corresponding to collision experiments and the physics of the early uni- a number of wounded nucleons between 60 and 250. verse. It is generally believed that the latter underwent Strangeness production at lower beam energy. also the phase transition from a deconfined quark-gluon plasma to normal nuclear matter. The temperatures In 1999 NA57 has taken data at 40 AGeV for both Pb- mentioned above indicate that, within the framework Pb and p-Be collisions. For the Pb-Pb data the Λ, Λ¯, Ξ of the standard Big Bang model, such a phase tran- and Ξ¯ signals could be extracted and the Λ/Λ¯ and Ξ/Ξ¯ − sition has occurred about 10 5 saftertheBigBang ratios were calculated [11]. Table 6.1 shows the values corresponding to a temperature of about 1012 K. found by NA57 together with the ratios published by 6.3 Strange baryon production in NA57 WA97 forthe158 AGeV data [12]. For the lower beam energy the Λ/Λ¯ and the Ξ/Ξ¯ ratios are smaller than for The NA57 experiment has been designed to study the the higher beam energy by factors ∼6 and ∼3respec- production of strange baryons and anti-baryons in p- tively. An increase of the anti-hyperon over hyperon Be and Pb-Pb collisions at the CERN SPS. It intends ratios with increasing beam energy is expected if the to extend the scope of its predecessor, the WA97 ex- baryon density of the state formed in the collision is periment, which observed an enhanced production of reduced. However, the values from NA57 are not yet strange particles in Pb-Pb collisions with respect to p- corrected for acceptance and efficiency. The final result Acollisions at 158 AGeV beam energy [8]. This en- will be produced in 2002. The comparison to proton hanced production is more pronounced for particles with induced reactions will be made soon, using the data alargerstrangeness content, yielding a maximum of a collected in the summer of 2001. The combined statis- factor 15 for Ω+Ω¯.This behaviour is in accordance tics of the WA97 and NA57 experiments will improve with predictions, where the strangeness enhancement is the errors significantly.

36 Enhancement versus centrality 10 The production yields for hyperons in proton-nucleus Ξ - collisions can be extrapolated to the yield for nucleus- nucleus collisions by scaling with the number of wounded nucleons in the system. Dividing the measured hyperon relative to p-Be w yields by the scaled p-Be yields shows that the sim- Λ ple scaling law does not predict the measured hyperon yields. The obtained ratios, separated in five centrality classes, are shown in figure A6 for the Λ, Ξ and their anti-particles. For comparison the results from the WA97 are also shown. The dashed lines in the fig- / N Yield per event 1 ure are predictions by a recently published canonical Pb-Pb statistical model [14] for the strangeness enhancement, 0I to IV p-Be which reproduces the WA97 results. This model pre- 2 3 1 10 10 10 dicts a saturation of the yield down to Nwound = 20. Number of wounded nucleons It can be noted that the preliminary NA57 yields for the Ξ and Ξ¯ are larger than the yields measured by WA97 [11]. This systematic difference is currently un- 10 der investigation. Furthermore the Λ yields are increasing as a function of the number of wounded nucleons, while the WA97 results are constant in the four most Ξ + relative to p-Be central collision classes [13]. Therefore it is too early to w draw conclusions from the data. However, if the NA57 results are confirmed then the striking drop in the Ξ¯ yield (3.5 σ)possibly indicates a change in the production mechanisms, in contradiction with the predictions of the model. This could indicate that in smaller col- Λ Yield per event / N Yield per event lision systems not enough energy is available for the 1 creation of a QGP, whilst it could have been created in Pb-Pb 0I to IV larger systems. p-Be 2 3 1 10 10 10 6.4 Strangeness and Charm Production in Number of wounded nucleons NA49 The aim of theNA49experiment attheCERNSPS Figure 6.3: Strange particle yield per wounded nucleon is a comprehensive study of hadronic reactions rang- in Pb-Pb relative to p-Be as a function of the number of ing from elementaryproton-proton (p − p)viaproton- wounded nucleons. The open symbols depict the WA97 nucleus (p − A)toheavyion(A − A)interactions. One results, the closed are fromNA57. The lines show the of the main motivations for this study is a critical in- predicition of a statistical model (see text). vestigation of the hypothesis that a quark-gluon plasma (QGP) state of matter is created in the early stage of central Pb-Pb collisions at the highest SPS energy of 158 AGeV. The data collected thus far by the various The NA49 detector [15] consists of four Large Volume experiments at the CERN SPS are indeed consistent Time Projection Chambers (VTPCs). Two of these with this hypothesis. This immediately raises the ques- VTPCs are placed behind each other downstream of tion if a transition point can be experimentally observed the target in a magnetic field. This allows for a sepa- by varying the collision energy or the size of the inter- ration of positively and negatively charged tracks and acting nuclei. For this purpose NA49 has taken central foranaccurate measurement of their momenta; about Pb-Pb data at different beam energies of 40, 80 and a 1000 charged tracks are routinely reconstructed in a 158 AGeV. Also recorded were 158 AGeV data with 158 AGeV central Pb-Pb event. The other two TPCs different colliding systems (p − p,C-C,Pb-Pb)atvar- are placed behind the magnet left and right of the beam ious centralities. line. These MTPCs increase the lever arm of the track reconstruction and are optimised to provide particle

37 〉 〉 25 2 π 〈 w Difference )/ N (A+A)-(p+p) 〉 0.3 〈 1 / K 〈 〉 20 + π 〉 〈 0 Λ 15 〈 -1 0.2 012345 1/2 F (GeV ) =(1.6 s

10 E NA49 Bevalac + Dubna 0.1 5 AGS RHIC p+p, p+p 0 051015 0 1/2 0246 F (GeV ) 1/2 F (GeV )

Figure 6.4: The pion multiplicity per wounded nucleon versus the Fermi energy measure (F) for central A-A Figure 6.5: The ratio of strangeness to pion yields ver- collisions (full symbols) and inelastic p-p interactions sus the Fermi energy measure (F) for central A-A col- (open symbols). lisions measured at the AGS (triangles) and by NA49 (squares). Also shown are the results from inelastic p-p interactions (open circles). The curve corresponds to a identification through a measurement of the specific prediction of a statistical model assuming√ a crossing of energy loss (dE/dx). At central rapidity the particle the threshold for QGP formation at s ≈ 9 AGeV. identification is further improved by a measurement of the time-of-flight with 60 ps resolution. The centrality of A−A collisions is measured by the energy deposition model [16] of the early stage of the reaction assum- of spectator nucleons in a downstream calorimeter. ing the transition to a phase of deconfined matter at Within the large and diverse physics programme of SPS energies (curves in Fig. 6.4). However, statistical NA49, NIKHEF participates in the analysis of the en- hadron gas models [17] can also qualitatively explain ergy dependence of strangeness production in central the trend observed in the data. It is foreseen to com- Pb-Pb collisions as well as in a search for open charm plete the energy scan in 2002 with Pb-Pb runs at 20 production in Pb-Pb events at the highest SPS energy. and 30 AGeV incidentenergy. Figure 6.4 shows the pion yield per wounded nucleon The study of open charm production in heavy ion col- versus the collision energy (expressed by Fermi’s mea- lisions is of considerable interest because the yield ex- sure F ∝ s1/4)measured in heavy ion collisions (full pected from statistical production of charm in equilib- symbols) and p-p interactions (open symbols). It can rium with a hot QGP[16]ismorethan an order of be seen that in the SPS energy range the pion multi- magnitude larger than that predicted from perturba- plicity starts to increase faster in nucleus-nucleus than tive QCD based calculations (see Fig. 6.6). To date, in nucleon-nucleon collisions. The strangeness to pion no measurement of open charm yields (D0 and D¯ 0 in ratio measured in A−A and p−p collisions is plotted as the present analysis) in heavy ion collisions exists. To afunction of F in Fig. 6.5. One observes that this ratio search for an open charm signal in central Pb-Pb col- increases at the lower AGS energies followed by a de- lisions at 158 AGeV, NA49 has taken a large statistics creasing trend at the SPS. This non-monotonic energy sample of 3M events in the year 2000. The analysis dependence is not seen in elementary p − p collisions. of the total sample of 4M events is currently being Both the steepening of the increase of pion produc- finalised. Because NA49 has no capability to detect tion and the saturation of the strangeness to pion ra- the secondary vertices of the D0 → Kπ decay, the tio at large energies can be understood in a statistical search proceeds through an analysis of the invariant

38 pling of front-end electronics and silicon detector was retained thanks to the aluminium microcables, at the cost of a more complicated module assembly procedure. 10 The module can be cooled by either water or ﬂuorcar-

(95% CL) bonmonophase coolants, without net dissipation in the

〉 QGP (T=265 MeV) 0 air. the overall electronics design (HAL25, hybrid, ca-

D bles and EndCap) was optimised to reduce the number + 0 ’99 result of additional discrete components. The fully diﬀeren- D

〈 tial output will improve the signal-to-noise ratio, even ALCOR at reduced voltages due to the IBM25 technology. Pro- totypes of various types of microcable were produced present result and assembly methods were worked out to the extent 1 that industry could start producing a test series of hybrids.

Upper limit statistical coalescence Another important event was the tendering procedure for the detectors. Three companies were selected and pQCD, A 4/3 scaling production will start early 2002, with delivery continuing into 2003. Testing procedures for both detectors and modules are being worked out. In Utrecht a mi- -1 croscanning (3 µm) set-up using infra-red light was re- 10 5 6 7 alised. This set-up can measure the charge collection 10 10 10 both between neighbouring strips on both sides of the N detector and between P- and N- sides as a function of Events the particle position. This knowledge can be used to improve the spatial resolution and to spot malfunction- ing strips. Figure 6.6: Preliminary upper limit of the D0 +D¯ 0 production yield per central Pb-Pb event at 158 AGeV in- The EndCap modules take care of buffering the front- cident energy (full square) compared to the predictions end signals, the power regulation and the front-end from various models (horizontal bands). Also shown is control. Moreover, the front-end electronics being at the upper limit obtained from the 1999 data (full circle) two different voltage levels (corresponding to the P and the sensitivity as function of the number of events and N strips), the EndCap also translates the signals analyzed (full line). to the same reference. Two ASICs (ALABUF and AL- CAPONE) are foreseen in the same IBM 0.25 µmtech- nology as the HAL25 front-end ASIC. Both were fully mass spectra of all pairs of positively and negatively designed and partly submitted in two engeneering runs. charged tracks in the event using, of course, the par- Excessive power consumption, due to the use of stan- ticle identification capabilities of the detector to sup- dard libraries, necessitates additional engeneering runs press as much aspossible the large combinatorial back- in 2002, as is the case with the HAL25. Test set-ups ground. Presently no signal is observed in the D0 mass for all these are being realised. window resulting in an upper limit of at most 1.5 pro- For the assembly of the detector modules on the carbon 0 ¯ 0 duced D and D per event, see Fig. 6.6. This re- fibre frames a robot was designed. The main purpose sult, although still preliminary, clearly excludes statis- of this robot is to automate the fine positioning of the tical charm production in equilibrium with a QGP, in 2000 detectors. The development of the motion control contrast to strangeness production. Indeed, the equi- software and the calibration of the complete system libration time of charm is expected to be much longer aredone by a commercial company. Design work on than that of strangeness due the larger mass. some details, like handling of the detector modules, will 6.5 The Alice experiment continue in 2002. In 2001 the design of the silicon strip module, based The production of thecarbonfibreframesinSt.Peters- upon the the newly designed front-end ASIC (HAL25), burg is approximately half-way. A set-up to measure was completed. In this design the mechanical decou- the mechanical properties of these frames was tested.

39 These properties, like rigidities in all axes, are needed to predict the sagging of the detector ladders: once mounted inside the ITS this sag cannot be measured.

References

[1]WA98collaboration, CERN/SPSLC 91-17 (1991). [2] WA98 collaboration, Phys. Rev. Lett. 85 (2000) 3595. WA98 collaboration, nucl-ex/0006007. [3] N. van Eijndhoven, Nucl. Phys. A618 (1997) 330. [4] J. Kapusta, et al.,Phys.Rev.D44 (1991) 2774. R. Baier, et al.,Z.Phys.C53 (1992) 433. P.V. Ruuskanen, Nucl. Phys. A544 (1992) 169c. [5] D. Steffen and M. Thoma, Phys. Lett. B510 (2001) 98. [6] J. Cleymans, private communication. [7] J.B. Bjorken, Phys. Rev. D27 (1983) 140. [8] E.Andersen et al.,CERN-EP/98-64. [9] P.Koch, B.Müller and J.Rafelski, Phys. Rep. 142 (1986) 167. [10] F. Antinori et al.,Eur. Phys. J. C 18 (2000) 57-63. [11] N. Carrer for the NA57 collaboration, Quark Mat- ter 2001,Long Island (2001). [12] R.Caliandro et al.,J.Phys.G:Nucl.Part.Phys. 25 (1999) 171. [13] Peter van de Ven, Ph.D.thesis, Utrecht University, The Netherlands (2001). [14] S.Hamieh, K.Redlich and A.Tounsi, Phys. Lett. B486(2000) 61-66. [15] NA49 Collab., S.Afanasiev et al.,Nucl.Instr. Meth. A430 (1999) 210. [16] M. Gazdzicki and M. Gorenstein, Acta Phys. Pol. B30 (1999) 2705. [17] J. Cleymans and K. Redlich, Phys. Rev. C60 (1999) 054908. [18] P. Lévai et al., nucl-th/0011023. [19] M. Gorenstein et al.,Phys.Lett. B509 (2001) 277.

40 7HERMES

7.1 Introduction Several guests were hostedbytheNIKHEF/VUA group in the year 2001. In the first half of the year Dr. The HERMES experiment at DESY studies the spin Moskov Amarian (Rome and Yerevan) shared his ex- structure of the nucleon with polarised targets that are tensive knowledge on charm production with us. In internal to the HERA electron/positron ring. the months July and August, a foreign undergraduate, In theyear 2001 no data were collected by the HER- Michiel Demey, worked as a summer student in our MES experiment, because of an upgrade of the HERA group. In the fall our group participated in a project on collider. As a result the emphasis of the activities of the ‘arbeidsorientatie’ for high-school students. All these HERMES collaboration was on data analysis and detec- projects were successfully concluded. tor development. This change in emphasis as compared Near the end of the year the upgraded HERA collider to previous years was reflected in the work carried out was commissioned. During these commissioning runs by the NIKHEF/VUA group in Amsterdam. the HERMES experiment was checked out, demonstrat- The year 2001 also marked the completion of the con- ing that the entire experiment is operational again. Un- struction of the Lambda Wheels, a wheel-shaped array fortunately, the HERA commissioning has not yet re- of silicon detectors, which was largely developed and sulted in stable high-intensity lepton beams, which are built at NIKHEF. In the spring the entire instrument required for experimentation at HERMES. It is expected was successfully installed in the HERMES experimental that data taking at HERMES will be resumed in the first set-up at DESY. Afterwards, the silicon modules were half of the year 2002. taken out again in order to avoid the large radiation 7.2 Physics analysis load to which the modules would be exposed during the commissioning of the upgraded HERA collider. A In this section several preliminary analysis results are large radiation load will lead to a dramatic increase presented that have been obtained by the HERMES of the leakage currents and a corresponding reduction collaboration in the year 2001. The subjects were taken of the life time of the silicon detectors. In order to from analyses with a large NIKHEF/VUA involvement. reduce the radiation load during normal operations a The spin structure of the nucleon dedicated Beam-Loss Monitor (BLM) was developed and constructed by the HERMES group in 2001. This From measurements of the proton spin structure func- p 2 monitor will provide a trigger signal if the HERA beam tion g1 (x, Q ) it has been learned that the spin carried starts to diverge from the desired orbit. The trigger by the quarks can only partly account for the total spin signal will be sent to a kicker magnet that was installed of the nucleon. Consequently, it is expected that glu- in the HERA ring in 2001. The BLM was installed and ons and possibly even the orbital angular momentum successfully tested at HERMES in the fall of this year. of quarks and gluons also contribute to the spin of the nucleon. For that reason it has been tried to obtain The analysis of HERMES data that were obtained in the information on the gluon polarisation in the proton. At period 1995 to 2000 yielded several prominent results. HERMES a first (somewhat model-dependent) result Two publications should be mentioned in this respect: was obtained from data collected on a longitudinally (i) the first observation on a polarised hydrogen tar- polarised hydrogen target in 1996 and 1997. A neg- get of Compton scattering at the quark level (known ative asymmetry was observed for events containing a as Deeply-Virtual Compton scattering or DVCS); and pair of oppositely charged high-p hadrons if a suffi- (ii) the first observation of single-spin azimuthal asym- T ciently large value of the transverse momentum p of metries in the production of neutral and charged pions. T each hadron is required. The negative asymmetry could The former result is important as data of this type give be interpreted in terms of apositive gluon polarisation access to the recently introduced generalised parton dis- ∆G/G =0.41± 0.18, if it is assumed that the two tributions, which contain information on dynamic corre- hadrons are produced by photon-gluon fusion (PGF). lations between different partons. The latter result implies that the only unmeasured leading-order structure The analysis has been repeated using the new data col- function, i.e. the transversity distribution h1(x),isnon- lected in the years 1998, 1999 and 2000, on a lon- zero. Both publications represent a proof-of-principle, gitudinally polarised deuterium target. Unfortunately, which will be followed by more precise measurements the expected asymmetry is smaller for this isoscalar of this kind in the future. target since the requirement of an oppositely charged

41 ) ) 1.1 h- h+ 1 1 T T d

0.8 ,p 0.8 σ ,p

h- 0.6 h+ 0.6 HERMES 96-00 preliminary T T p

(p 0.4 (p 0.4 σ || ||

A 0.2 A 0.2 world data parameterisation 0 0 -0.2 -0.2 1 -0.4 -0.4 -0.6 -0.6 -0.8 -0.8 -1 -1 0.5 1 1.5 2 0.5 1 1.5 2 p h+ (GeV/c) p h- (GeV/c) T T 0.9 ) ) 2 π h2 1 1 T T 0.8 0.8 ,p ,p 1 π h1 0.6 0.6 T T 0.4 0.4 (p (p || || 0.2 0.2 A A 0.8 0 0 -0.2 -0.2 -0.4 -0.4 -0.6 -0.6 -0.8 -0.8 -1 -1 0.5 1 1.5 2 0.5 1 1.5 2 0.7 p h2 (GeV/c) p π2 (GeV/c) -2 -1 T T 10 10 1 x

Figure 7.1: Measured target-spin asymmetry A for the production of two high-momentum hadrons from a lon- Figure 7.2: Ratio of inclusive deep-inelastic scattering gitudinally polarised deuterium target. In the upper left cross sections on deuterium over hydrogen versus the (right) panel the asymmetry is shown as a function of Bjorken scaling variable x. The curve corresponds to a parameterisation of existing data, mainly those reported the transverse momentum pT of the positive (negative) hadron while the momentum of the negative (positive) by NMC. The band at the bottom part of the plot is larger than 1.5 (GeV/c)2.Inthe lower left panel the represents the systematic uncertainty of the data. same is plotted for a leading hadron (‘h1’) versus the pT of the next-to-leading hadron (‘h2’), and in the lower right panel the same asymmetry is shown for identified adding the data for the two different spin orientations. pions. Of particular interest is the ratio of neutron and proton n p structure functions F2 /F2 ,forwhichveryprecise data have been published by NMC. As the HERMES data were obtained at a much lower incident lepton energy, hadron pair is less effective on deuterium. This can the comparison of the two data sets can be used to be understood from the positive charge of the proton, extract information on R = σ /σ (at small x) and on which enhances the probability of detecting two equally L T higher-twist effects (at large x). These dataextendthe charged (positive) hadrons stemming from the compet- (x,Q2)-range of existing measurements of ∆R = Rp − ing QCD Compton process. Hence, by requiring oppo- Rn,whichisveryimportant as the value of Rp and Rn sitely charged hadrons the QCD Compton contribution enters in many analyses. Possible higher-twist effects is suppressed on the proton as compared to the PGF at large x are of considerable interest as well, since it process. However, since the neutron is uncharged, this has always been very difficult to identify unambiguous requirement is much less effective when trying to iden- evidence for such effects. At large x both the HERMES tify the PGF process on a deuteron target. As a re- and the NMC data are largely dominated by the F (x) sult the expected asymmetry is less. This is confirmed 2 contribution (rather than the R-contribution, which is by the data shown in Fig. 7.1. Detailed Monte-Carlo more important at small x), thus enabling such a study. studies are needed to compare the proton and deuteron results in a more quantitative fashion. The preliminary data for the Deep-Inelastic Scattering (DIS) cross-section ratio σd /σp are shown in Fig. 7.2. The structure-function ratio F n/F p 2 2 Under the assumption that ∆R = Rp − Rn = 0, the The data collected for studies of the spin structure of cross-section ratio equals the structure-function ratio. the nucleon can also be used to obtain information on The data are in reasonable agreement with a parameter- 2 the spin-independent structure function F2(x, Q ) by isation of the existing data, in particular in the mid-x

42 range. At small x the data are somewhat below the Combining all data obtained in those three years (cor- parameterisation, but the deviation is smaller than the responding to roughly 8 million DIS events), a search preliminary estimate of the statistical and systematic for ΛC baryons was undertaken. The search was based + uncertainty. A similar situation occurs at large x,where on the ΛC → Λ+π decay, which has a branching the deviation is also smaller than the presently esti- ratio of only 0.9%. In the analysis the events are re- mated systematic uncertainty. It is clear from these pre- quired to contain at least three hadrons. Using the liminary data that neither the deviation from ∆R = 0 particle identification capabilities of the HERMES Ring nor the higher-twist effects can be very large. This is Imaging Cerenkov˘ (RICH) detector, the hadrons must remarkable since the present data correspond to Q2- be identified as a proton and (at least) two pions. By values which are on average about a factor of 5 below combining the four-momenta of the proton and the pion those covered by the NMC data. a Λ0-peak is easily found in the pπ-invariant mass spectrum. The reconstructed four-momentum of the Λ0 hy- Photoproduction of Ξ and Λ baryons. C peron is usedtoevaluatetheinvariant mass of Λ0 − π In an effort to obtain complementary information on the pairs. By also requiring that the transverse momen- Λ 0 spin structure of the nucleon, it could be very interest- tum pT of the Λ hyperon with respect to the prop- ing tosearchforΞ and ΛC baryons. The Ξ hyperon agation direction of the assumed ΛC baryon is large Λ contains two strange quarks, and can thus be used as a (0.6 GeV/c < pT < 0.88 GeV/c), the spectra shown probe of the strange sea,while the charmed ΛC baryon in Fig. 7.3 are obtained. While no structures are ob- − –if produced by photon-gluon fusion– provides informa- served in the Λ0π -spectrum, a clear peak is seen in 0 + tion on the gluon polarisation. For those reasons it has the Λ π -spectrum at the location of the known ΛC been tried to identify Ξ and ΛC baryons in photopro- mass. duction data that were collected at HERMES in the Although this result represents the first observation of years 1998, 1999 and 2000 on a polarised deuterium a Λ baryon in a polarised deep-inelastic scattering ex- target. C periment, the number of observed events is insufficient to evaluate a the asymmetry of the yield with respect to 40 the orientation of the target spin. In order to increase the number of events containing a ΛC baryon, it has 35 also been tried to consider partially reconstructed Λ Λ+ C C PDG-value 0 + events. Since the branching ratio ΛC → Λ +π +X is 30 about 10%, an analysis of the Λ0π+-spectrum at lower Λ0+π+ invariant mass will yield considerably more events. This 25 Λ0+π- analysis is in progress.

As a by-product of the ΛC search, very clear evidence 20 for the production of Ξ hyperons was obtained. The results are shown in Fig. 7.4. The Ξ hyperon has a 15 branching ratio of close to 100% into a Λπ-pair. Hence, its observation is considerably favoured as compared to 10 + − the observation of a ΛC baryon. In fact, both the Ξ and its anti-particle the Ξ¯+ hyperon are observed. The 5 latter particle, which has a (d¯¯s¯s)structure, is an ‘all- sea’ object. Its production in an experiment with both 0 2.2 2.3 2.4 2.5 2.6 2.7 beam and targetpolarised,will make it possible to ob- M(Λ,π) [ GeV ] tain information on the sea-quark polarisation. The determination of the target-spin asymmetry for the Ξ hyperons is underway. Furthermore, Monte-Carlo sim- Figure 7.3: Mass spectrum for photo-produced Λ-π ulations were begun to study the importance of com- pairs. The upper (lower) histogram corresponds to the peting production mechanisms. use of positive (negative) pions in the analysis. In both Nuclear eﬀects cases the transverse momentum pT of the Λ hyperon + with respect to the ΛC direction is required to be be- During selected (brief) periods the HERMES experi- tween 0.6 and 0.88 GeV/c. ment has been operated with unpolarised nuclear tar-

43 450 R 400 1.2 350 300 250 200 1.1 150 100 50 0 1 0.16 0.18 0.2 0.22 0.24 0.26 M(Ξ-)-M(Λ0) [ GeV ] 0.9 100

80 0.8 60

40 0.7 20

0 10 -2 10 -1 1 0.16 0.18 0.2 0.22 0.24 0.26 2 − p 2 [GeV ] M(Ξ+)-M(Λ0) [ GeV ] T

Figure 7.4: Yield of photo-produced Λπ-pairs as a func- Figure 7.5: Ratio of semi-inclusively produced hadrons tion of the invariant mass of the pair. The recon- on a heavy nucleus with respect to deuterium as a func- structed mass of the Λ hyperon has been subtracted tion of the transverse momentum squared of the emit- fromthe invariant mass. In the upper panel the results ted hadron. The closed circles represent the nitrogen are shown for Λ0π+-pairs, while the lower panel shows over deuterium data and the closed squares the krypton Λ¯0π−-data. In both cases a clear peak corresponding over deuterium data. to the production of a Ξ hyperon is observed.

nuclear ratios obtained at HERMES and other experiments largely disappeared. gets. These measurements have been used to study Fortunately, the inefficiencies caused by the photon the effect of the nuclear environment on the formation showers do not affect the semi-inclusive data quoted of hadrons, resulting in (indirect) determinations of the at the beginning of this section since the observation formation length ofhadronsand the coherence length of an additional hadron in the final states excludes con- of (qq¯)-fluctuations of the virtual photon. tributions from radiation produced in elastic scattering. In fact, the additional data collected on krypton en- Unexpectedly, these data also showed a difference be- abled us to extend our studies on the influence of the tween the ratio of inclusive DIS cross sections obtained nuclear environment on the hadronisation process to on nitrogen and deuterium as compared to similar nu- aheavier nucleus. Part of these results are shown in clear ratios obtained elsewhere at higher lepton ener- Fig. 7.5, where the hadron yields in a semi-inclusive gies. This difference has been attributed to a possible reaction on a heavy nucleus relative to those on deu- mass dependence of the ratio R = σ /σ of longitudi- L T terium are shown. It is observed that the ratio is more nal over transverse photo-absorption cross sections. In or less constant up to p2 ≈ 0.6 (GeV/c)2.Forlarger order to study this effect in more detail additional data T values of p2 ,thedata show a steep rise. on an even heavier nucleus, krypton, were collected. T 2 While analysing these data a serious experimental prob- The relativeriseofthepT -distributions in nuclei beyond 2 ≈ 2 lem was discovered. Bremsstrahlung photons radiated pT 1(GeV/c) has also been seen in proton-nucleus in elastic nuclear scattering may cause large showers in and nucleus-nucleus collisions, where it is known as the the frames of some of the tracking detectors, leading to Cronin effect. This effect has now also been observed large local inefficiencies. When corrected for these infor the first time in deep-inelastic scattering. The ef- efficiencies the previously reported differences between fect is assumed to arise from multiple scattering of the

44 3 struck quark (and/or the produced hadron) on its way 10 out of the nucleus. with rad. cor Other nuclear effects (such as possibly different forma- without rad. cor tion times for pions and protons) are presently under b/sr/GeV) study using the new krypton data. This data set has µ ( two advantages as compared to the (already published) e‘ 2 10 nitrogen data: the effects are larger, and the data were Ω d collected with the new RICH detector enabling the de- e‘ termination of the attenuation ratio for different hadron /dE species. σ 2 7.3 The JLab experiment d 10 In order to investigate the nuclear dependence of inclusive deep-inelastic scattering in a different domain, adedicated experiment was carried out at the Jeffer- son Laboratory (JLab) in Newport News, Virginia. The experiment (E99-118) was performed in Hall C in the summer of the year 2000 using electron beams of 2.301, 1 3.419 and 5.648 GeV, and an average electron current 00.511.5 2 2.5 3 3.5 4 4.5 5 of 25 µA. The scattered electrons were detected with E' (GeV) the High-Momentum Spectrometer. Data were taken at electron scattering angles between 10 and 60 degrees using six different targets: LH2,LD2,C,Al,CuandAu. Figure 7.6: Spectrum for inelastic electron scattering off a Cu target as obtained in Hall C at JLab. The Cross sections for deep-inelastic electron-nucleon and incident electron energy was 5.648 GeV, and the spec- electron-nucleus scattering were measured at small val- ◦ 2 trometer was located at an angle of 10.6 .Thedata ues of x and Q ,i.e.0.007 < x < 0.55 and 0.03 are shown both with and without radiative corrections. < Q2 < 2.8 (GeV/c)2.Thedata will be used to determine the cross-section ratio σA/σD .Asdatahave been collected at different beam energies it is possible rate description of all radiative corrections, both inter- to perform a Rosenbluth separation, which will yield nal and external ones. the ratio of longitudinal over transverse cross sections, R = σL/σT . 7.4 The Lambda Wheel project The analysis is in progress. Various efficiencies (track- In the last couple of years a new wheel-shaped silicon ing, Cerenkov,˘ Calorimeter) have been determined. The detector, known as the Lambda Wheels, has been de- density of the cryogenic targets has been corrected for veloped. The purpose of this detector is to increase the effect of local boiling under the influence of the the acceptance of the HERMES spectrometer for Λ0 beam. The charge-symmetric background has been hyperons and charmed particles, such that the polari- determined for all targets by measuring positron cross sation of strange quarks and gluons can be measured sections, obtained by reversing the polarity of the spec- with improved precision. Most of the development work trometer. Pion rejection was implemented in the hard- related to the construction of the Lambda Wheels was ware trigger, and the remaining pion background was carried out at NIKHEF. cut by using the information from the Cerenkov˘ and Calorimeter detectors. Near the beginning of 2001 the construction of the Lambda Wheels was completed. A few months later An example of the measured cross section with and the entire system was installed at HERMES, where it without radiative corrections applied is shown in Fig. 7.6. is located just downstream of the (polarised) internal As can been seen, the radiative corrections at low scat- target. The installation was fully successful, as illus- tered energy E are very large, which is largely due trated in Fig. 7.7 showing the front view of the in- to the radiation tail of elastically scattered electrons. stalled Lambda Wheels. After the installation the indi- Therefore, special attention must be paid to an accu- vidual detector modules were taken out again, in order to avoid radiation damage which usually occurs during

45 Support

2 cm

4 cm

Polystyrene block Gas volume

Electronic components 1 cm Printed circuit board

Figure 7.8: One side of the Beam Loss Monitor that wasinstalled at HERMES in 2001. The other side is similar to the side shown. The BLM consists of 3 polystyrene ionisation chambers, and one dummy. The dummy chamber is shown on the far right of the ﬁgure. Both the gas ﬂow, the support structure and a cross sectional view are shown.

Mons (Belgium). As a result the output of the BLM Figure 7.7: Photograph of the new wheel-shaped silicon can now be specified in units of Gy/s. detector at HERMES. The instrument is known under As the BLM is equipped with fast electronics, which the name Lambda Wheels. The picture was taken after are connected to the dump kicker by means of an 5 the test installation during the HERA shut down. Each km long optical fibre, it is possible to dump the HERA of the 12 individual silicon modules can be seen. beam within a few milliseconds. The BLM is the fastest beam-dump system of all HERA experiments. The BLM was installed in the summer of 2001, and is extensive beam-tuning efforts that are needed to com- fully operational since October. During the last months mission the upgraded HERA collider. It has been de- of the year it has operated stably. The trigger has not cided to wait until the commissioning of HERA is (more yet been connected to the fast kicker magnet in order to or less) finished before the Lambda Wheel modules will avoid interference with the HERA commissioning effort. be reinstalled. Using the BLM three types of beam loss events have been observed: (i) fast losses (within one HERA rev- It has been shown during tests of a prototype Lambda olution) causing very little radiation; (ii) losses spread Wheel module (in 2000) that unexpected beam losses, out over many hundreds of revolutions, which cause a may cause a significant increase in the leakage current fair amount of radiation; and (iii) slow losses, causing of the silicon detectors. In order to avoid such dam- asignificant amount of excess radiation. The BLM is age to accumulate, it was decided to build a dedicated able to dump the beam for the last two event classes. Beam Loss Monitor (BLM) that will create a trigger signal if excessive radiation levels are observed. The 7.5 Longitudinal Polarimeter trigger signal will fire a newly installed HERA kicker Since early 2001 our group is in part responsible for the magnet in order to dump the beam in a controlled fash- operation and maintenance of the HERMES longitudi- ion. nal polarimeter (LPOL). The polarimeter measures the The BLM consists of two sets of 3 ionisation chambers polarisation of the HERA lepton beam making use of (see Fig. 7.8) and one dummy detector of the same size. the asymmetry in the Compton cross section for scat- Atrigger is generated if 2 of the 3 chambers generate tering circularly polarised (laser) photons off polarised asignal (above threshold) while the dummy gives no leptons. The intersection point of the laser is located signal. In this way the dummy prevents false triggers 39 m downstream of the HERMES target. The back due to electromagnetic interference. After construction scattered photons are detected in a calorimeter that the BLM was calibrated at an intense X-ray source in measures the total energy of the photons. Due to the

46 very large boost of the photons, almost all photons are scattered into a very small cone around 180◦ in the laboratory frame and travel along the lepton beam. In order to separate the photons from the beam a dipole magnet bends the beam by 0.54 mrad, which is enough to extract the photons from the beam line 16 m downstream of this bend. The intensity of the laser beam and the lepton beam is such that the polarisation can be measured for separate electron bunches. In 2001 a new second calorimeter has been built, tested and installed. This calorimeter consists of scintillation plates sandwiched between tungsten plates with a total depth of 20.6 radiation length. This new calorimeter wastested at the DESY test beam facility with electrons from 1 to 6 GeV and at CERN with electrons between 10 and 30 GeV. The analysis of the data is in progress and preliminary results show that the response is linear with energy. Since the new calorimeter is not segmented an additional detector is needed to measure the distribution of the back scattered photons. For this purpose a scintillating fibre detector is needed, which will be located in front of the calorimeter. An improved scintillating fibre detector is presently under construction. 7.6 Outlook Following the HERA commissioning the Lambda Wheel modules will be installed at HERMES, and the trigger generated by the Beam Loss Monitor will be connected to the HERA dump kicker. Thereafter, the measurements at HERMES can be resumed. For the NIKHEF/VUA group initially the emphasis will be on the final commissioning of both the Lambda Wheels and the Beam Loss Monitor, while we also carry a shared responsibility for the operation of the longitudinal (beam) polarimeter. Data taking in the year 2002 will employ a polarised hydrogen target with its spin axis polarised perpendicu- larly (or transversely) to the beam. Such data will give access to the sofar unmeasured leading order structure function h1(x).Itisofconsiderable interest to ob- 2 tain data on h1(x),asitsscaling violations (or Q - dependence) are predicted to be dramatically different from those of the other leading-order structure functions. Moreover the integral over h1(x) will make it possible to determine the tensor charge of the nucleon, a quantity for which predictions exist based on lattice gauge theory.

47 End view of the Hermes transverse target magnet.

48 8ZEUS

8.1 Introduction (x) x=6.32E-5x=0.000102

10 x=0.000161 ZEUS NLO-QCD Fit This year HERA accumulated no luminosity. Due to the x=0.000253 tot. error -log

x=0.0004 em work on the luminosity upgrade the accelerator was shut 2 x=0.0005 F 5 x=0.000632 down until September. The upgrade entailed a com- x=0.0008 ZEUS 96/7 plete rework of the H1 and ZEUS intersection regions, x=0.0013 BCDMS where completely new final focus quadrupoles were in- E665 stalled significantly closer to the intersection points of x=0.0021 NMC 4 the electron and proton beams. This means for ZEUS x=0.0032 that these magnets are now inside the ZEUS detector. In the forward region the quadrupole magnet now pro- x=0.005 trudes to inside the forward tracker and in the rear it is x=0.008 installed inside the rear calorimeter. 3 The placing of these magnets gives a significant in- x=0.013 crease in the produced synchrotron radiation near the x=0.021 detector in the horizontal plane (due to early separa- x=0.032 tion of the beams). In order to allow the unhindered 2 passage of this radiation the beam-pipe needed to be x=0.05 redesigned. It now has an elliptical shape. At the same x=0.08 time the material from which this was manufactured x=0.13 was chosen to be an Al-Be alloy, which will significantly 1 x=0.18 reduce the amount of material particles need to traverse x=0.25 before being measured in the new micro-vertex detec- x=0.4 tor. x=0.65 At startup inSeptember the installed radiation moni- 0 2 3 4 5 tors in the ZEUS interaction region showed an intol- 1 10 10 10 10 10 erable background, presumably from synchrotron radi- Q2(GeV2) ation. Significant machine studies in the last months of the year pinned down the source of this radiation Figure 8.1: The F2 structure function as a function of to a bending magnet in the electron ring some ninety Q2 for various values of x. metres from the intersection region. To reduce the flux of radiation two new collimators have been designed and ordered. They will be ready for installation in the atic and statistical accuracy. Much work was invested in machine at the beginning of 2002. the correct description of correlated systematic errors. These are of significant importance when interpreting It was also determined that a collimator that is placed the dataintermsofQCDevolution of parton densities downstream of the detector was dimensioned too small, in the proton. The analysis of the data in terms of so that this could be a source of backscattered syn- the QCD DGLAP evolution equations provided confir- chrotron radiation in the detector. This has in the mation of the previous results that the structure of the meantime been enlarged. Several other modifications in proton can be described by perturbative QCD down to other parts of the accelerator will also be performed at four-momentum transfer squared, Q2,valuesofabout thebeginning of 2002. With these modifications there 1GeV2. is good hope that the machine will start producing high luminosity running towards March 2002. The precision with which the parton densities can be extracted from the data has followed the data precision. 8.2 Structure Function F2 Figure 8.1 shows the structure function F2 as a function The work of the NIKHEF group in ZEUS continued on of Q2 for several values of x,thefraction of the proton the extraction of the structure function F2 of the pro- four-momentum carried by the struck quark. A fit to ton. It culminated in a publication. The present results the data in terms of the DGLAP evolution equations surpass the previously published results in both system- is also shown. Especially noteworthy is the precision

49 em 2 2 2 2 2 2 ZEUS 2 Q =3000 GeV Q =5000 GeV Q =8000 GeV ) F

ZEUS 96/97 2 NLO QCD Fit 0.75 CTEQ4D x=1.e-4 xg(x,Q 0.5 x=0.001 20 0.25

Q2=12000 GeV2 Q2=20000 GeV2 Q2=30000 GeV2

0.75 15 ZEUS NLO-QCD Fit

0.5 α tot. error ( s -free Fit) α tot. error ( s -fixed Fit) 0.25 10

0 -1 -1 -1 10 10 10 1 x x=0.01 5 Figure 8.2: The F2 structure function as a function of xathighQ2.

x=0.1 obtained for very large Q2 values (Fig. 8.2). Figure 8.3 0 shows the gluon density extracted from the fit as a function of Q2 for several values of x. 2 3 4 Especially the evolution of the gluon density at x = 1 10 10 10 10 2 2 10−4 is striking. Both the extremely steep rise and the Q (GeV ) fact that the density drops below zero for Q2 < 1GeV2 has been the subject of much controversy. Although Figure 8.3: The gluon density in the proton as extracted the fit to the data provides an excellent description of from a NLO QCD fit to the data ontheF2 structure the structure function over a very wide range in x and function. Q2 the present precision of the data indicates that the extension of the fits to include the very low Q2 data is no longer possible as it leads to a very large increase in the χ2 of thefit. has been a major responsibility of the group, not only in hardware but also in the tracking software. The con- Figure 8.4 shows a comparison of the fit, performed on struction of the detector was finalised at NIKHEF and data with Q2 > 2.5GeV2,totheZEUS data for Q2 < the detector was shipped in two halves to DESY for 1GeV2.Increasingly large deviations from the fits are afullsystemtestinMarch.Priortothe installation observed as Q2 decreases, indicating the breakdown of in the ZEUS detector, the two vertex detector halves the description of the structure of the proton in terms were build together around the new beampipe. Then of parton densities evolving according to perturbative it was fully equipped and several weeks of cosmic ray QCD. This is of course not surprising. It is the fact that data were taken. the data deviates from this perturbative description only at such low values of Q2 that is the real surprise. From this system test it could be concluded that, in all, 8.3 Micro-Vertex Detector more than 99 percent of the 207360 channels performed according to specification. After completion of the cos- Apart from the ongoing physics analyses the major ef- mic ray test run the vertex detector was inserted in the fort of the NIKHEF group wasthisyearconcentrated ZEUS detector. The system has again been tested after on the finalisation of the micro-vertex detector. This installation using cosmic rays. This time the ZEUS cen-

50 ZEUS events are available for testing the track-ﬁtting pack- 2 Q2=0.3 GeV2 Q2=0.4 GeV2 Q2=0.5 GeV2 age. Figure 8.5b shows a typical example of the perfor- 1.5 mance of the ﬁtting package. With this new detector and the foreseen increase of luminosity we look forward 1 to several years of exciting physics. 0.5 0

em 2 2 2 2 2 2 2 2

F Q =0.585 GeV Q =0.65 GeV Q =0.8 GeV 1.5 1 0.5 0 a 2 Q2=1.5 GeV2 Q2=2.7 GeV2 Q2=3.5 GeV2 1.5 1 0.5 0 2 2 2 2 -5 -3 -1 2 Q =4.5 GeV Q =6.5 GeV 10 10 10 1

1.5 ZEUS NLO-QCD Fit tot. error 1 ZEUS 96/7 0.5 ZEUS BPT 97 BCDMS E665 0 NMC -5 -3 -1 -5 -3 -1 10 10 10 110 10 10 1 ZEUS SVX X

Figure 8.4: The prediction from the ﬁt performed at 2 2 Q > 2.5 GeV of the F2 structure function at very low Q2 compared to ZEUS data. b

tral tracker which surrounds the micro-vertex detector was also activated and the magnetic field was turned on. This allowed a first test of the Kalman Filter track- fitting software which has been developed at NIKHEF (see Fig. 8.5a). This package written in the object oriented language C++ performed without problems even when incorporated in the standard ZEUS software environment, that is predominantly written in FORTRAN. The cosmic ray test showed that the micro-vertex detector was positioned within 1 mm of the nominal position. Further alignment of the detector with respect to the central tracker is ongoing. Figure 8.5: (a) A cosmic ray muon reconstructed in the Finally the Monte-Carlo description of the micro vertex micro-vertex detector.(b) A typical Monte Carlo neutral has been completed and after tests with single parti- current deep inelastic scattering event. cles now many neutral current deep inelastic scattering

51 The two detector halves of the ZEUS vertex detector are ’mated’ for the very ﬁrst time.

52 BLEP in 2001 1DELPHI

1.1 End of data taking and reprocessing Inclusive vertices and soft leptons The DELPHI detector stopped data taking on the 2nd 0.6 of November 2000. The dismantling of the two end- caps and a large fraction of the Barrel Muon Chambers 1992-2000 data started the end of that month and was completed end of May 2001. The other part of the detector and some of its muon chambers remain in pit 8 and serve as a permanent exhibition for visitors. fraction of like-sign events 0.5 The final reprocessing of all LEP2 data taken in 1997- 2000, using the latest detector calibrations, alignments and the final version of the reconstruction software, was started onJune 1st and continued until September 21st. The reprocessing of the much smaller sample of 1996 data was done during the first week of November. In 0.4 addition, about 170 million Monte-Carlo events have been generated in 2001.

1.2 Selected research topics 024681012 Atotalof 18 papers were published in physics journals proper time (ps) by theDELPHI Collaboration in 2001. Fifty papers were submitted to the EPS Conference in Budapest and Figure 1.1: Fraction of like sign events as a function of to Lepton Photon 2001 in Rome, of which 12 contribu- the reconstructed proper time. The points with error tions were based exclusively on LEP1 data and 38 on bars correspond to the data, the continuous line to the LEP2 data. ﬁt result. The NIKHEF group contributed to B and τ physics, W physics and Triple Gauge Couplings (TGC’s), measure- P(B0 → B0)= ment of the ZZ cross section and to the Higgs search. d d Γd −Γd t ∆Γd Two PhD theses were completed: one on kaon produc- 2 e [cosh( 2 t)+ cos(∆md t)]. tion in τ decays and one on the measurement of the W ΓH +ΓL boson mass. d d H − L Here Γd = 2 , ∆Γd =Γd Γd , and H − L Four studies by our NIKHEF group, will be discussed ∆md = md md ,whereH and L denote respectively here. the heavy and light physical states.

0 − 0 The width difference |∆Γd |/Γd is expected to be much 1.3 Bd Bd oscillations smaller than 0.01. The mass difference ∆md is propor- 2 Neutral B meson oscillations were studied using a total tional to CKM matrix element |Vtd | . sample of about 4.0 million hadronic Z decays regis- trated by the DELPHI detector between 1992 and 2000. In the analysis a sample of 155k soft leptons, i.e. identified electrons and muons with a transversemomentum 0 − 0 In the Standard Model, Bd Bd mixing is a direct con- of less than 1.2 GeV/c, and a sample of 615k inclusively sequence of second order weak interactions. Starting reconstructed secondary vertices were selected. with a B0 meson produced at time t=0, the probabil- d From the flight distance and the estimated momentum, ity, P,toobserveaB0 decaying at the proper time t d the reconstructed proper time was determined. At the can be written, neglecting effects from CP violation: Z pole bb¯ quark pairs are produced back to back. The event is separated into two hemispheres where the b or b¯ charge was estimated from several discriminating

53 DELPHI preliminary - -

) 81

2 Ð Ð e Z e Z 80.8 Hadronic channel ( qqqq ) χ2/ndf = 0.90 80.6 80.4 80.2 e e 80 W mass (GeV/c 79.8 Systematical Statistical + + 79.6 e Z e Z 170 175 180 185 190 195 200 205 210 Centre of mass energy (GeV) DELPHI preliminary Figure 1.3: The NC02 diagrams describing ZZ boson

) 81 2 Ð νÐ pair production. 80.8 Semi-leptonic channel ( qql l ) χ2/ndf = 0.42 80.6 80.4 −1 80.2 0.007 ps .Itprovidesaprecise estimate of the fun- 80 damental CKM matrix element |V | and a test of the

W mass (GeV/c td 79.8 Systematical Statistical Standard Model. The measurement of the width differ- 79.6 ence is currently the best in the world. It will take some 170 175 180 185 190 195 200 205 210 time before the B factories will measure this quantity Centre of mass energy (GeV) more precisely. This measurement is an important test of our understanding of the Bd meson, as Heavy Quark Figure 1.2: Fitted W mass as a function of the centre- Effective Theory predicts the relative width difference of-mass energy in the fully-hadronic (top) and semi- to be less than 0.01. leptonic (bottom) WW decay channels. The statistical 1.4 W mass and width and systematic components of the combined W mass uncertainty are shown, where the shaded areas are pro- Preliminary values for the mass and width of the W portional to the ratio of the squares of the two compo- boson using all data collected in 1996-2000 were ob- nent errors. tained:

M = 80.401 ± 0.045 (stat) ± 0.034 (syst) variables. Events that mixwill lead to a like-sign (++ W ±0.029 (FSI) ± 0.017 (LEP) GeV/c2 or −−), while unmixed events give an unlike-sign (+− − or +)chargecombination. ΓW = 2.109 ± 0.099 (stat) ± 0.057 (syst) ± 2 The mass difference between the two physical states in 0.042 (FSI) GeV/c 0 − 0 the Bd Bd system was determined by fitting the fraction of like-sign tagged events as a function of the where FSI represents the uncertainty due to final state reconstructed proper time t as shown in Fig. 1.1. The interactions. The W mass results for each of the WW preliminary result is: decay channels obtained at the different centre-of-mass energies are fully compatible, as can be seen in Fig. 1.2. −1 Work is in progress to improve on the understanding of ∆md =(0.531 ± 0.025 (stat) ± 0.007 (syst.)) ps . the systematics. In the fit also the width difference between the heavy 1.5 ZZ cross section and light state was a free parameter. Using the mea- At centre-of-mass energies above 182.3 GeV two Z sured B lifetime τ =(1.55±0.03) ps, |∆Γ |/Γ = d Bd Bd Bd bosons can be produced according to the NC02 pro- 0.00±0.09(tot).Thefollowing preliminary upper limit cesses shown in Fig. 1.3. Because the Z can decay into was derived: quark-antiquark (q)orlepton-antilepton (l or ν)pairs five main final states can be analysed: qqq¯ q¯, l +l −qq¯, | | + − + − + − ∆ΓBd /ΓBd < 0.15 at 90% CL. νν¯qq¯, νν¯l l and l l l l where l = e,µ,τ.The NIKHEF group contributes to the analysis of the more The measurement of ∆md is the single most precise abundant four quark final state. By using a probabilis- measurement of this quantity at LEP. It is compati- tic technique to combine several discriminating vari- ble with the present world average of ∆md = 0.496 ± ables, the large background in the four quark channel

54 1.6 3 All Channels (1999-2000) 1.4 DELPHI PRELIMINARY 1.2 YFSZZ theoretical prediction DELPHI PRELIMINARY 1 HZ - FLAVOUR BLIND HYPOTHESIS

0.8 cross-section/SM 2 0.6 expected 95%CL exclusion observed 95%CL exclusion 0.4

NC02 CrossSection (pb) NC02 CrossSection 0.2

0 170 175 180 185 190 195 200 205 210 CMS Energy (GeV) 1

Figure 1.4: The ZZ cross section as a function of the centre-of-mass energy. The points witherror bars correspond to the data, the solid line to the Standard Model prediction. 0 60 80 100 mass(GeV) - from WW and qq¯γ) events - can be suppressed and an average signal purity of about 50% is reached. The Figure 1.5: Expected and observed upper limits on the selection efficiency is about 34%. The preliminary re- production cross section of a flavour blind Higgs as a sults for the NC02 ZZ cross section as a function of the function of the Higgs mass. centre-of-mass energy using all the channels is shown in Fig. 1.4. The Standard Model prediction using the YFSZZ generator is shown as a solid line. The results structed. Using simulation, the efficiency of the analysis are compatible with the Standard Model prediction and for Higgs decays into different quark pairs or gluons was limits on non-Standard Model γZZ and ZZZ couplings estimated as a function of the Higgs mass. will be derived. The combined results are summarised in Fig. 1.5. The 1.6 Flavour blind Higgs search observed and expected upper limit at 95% CL on the production cross section divided by the Standard Model The results of the search for the Standard Model Higgs Higgs cross section are shown as a function of the Higgs were published in 2001 and a lower limit on the mass mass. A more model independent - preliminary - lower of the Standard Model Higgs boson of 114.3 GeV/c2 limit on the Higgs mass was put at 109.9 GeV/c2. was set. An analysis was started to search for a Higgs decaying hadronically but not necessarily into bb¯ quarks. In the so-called flavour blind search, one is looking for a Higgs decaying into a quark-antiquark pair or gluons. It was assumed that the Higgs is produced as in the Standard Model, i.e. through Higgsstrahlung with an associated Z.Thesearchismotivated by Supersym- metric Theories where the Higgs decay into bb¯ quarks can be strongly suppressed and the Higgs decays e.g. predominantly into gluons. Final states with the Z decaying into quarks or leptons were selected. By applying a mass constraint on the Z decay products and the H decay products, the probability of an event to be compatible with a ZH decay is calculated. By combining this information with other discriminating variables a combined variable was con-

55 The L3 detector at the ‘old LEP’ accelerator.

56 2L3

2.1 Introduction Apart from the Higgs,theonlyparticle of the Standard Model not yet discovered, searches were performed for L3 was a general purpose detector designed with good particles which occur in various extensions of the Stan- spatial and energy resolution to measure electrons, photons, muons and jets produced in e+e− reactions. After the decision to close LEP, the L3 detector was 1 dismantled at the beginning of 2001, ending the period of yearly data-taking which began in 1989. This also meant the end of its detection of cosmic ray muons. However, the air shower array above L3 continued to -1 take data. 10 With no possibility of more data, the collaboration’s b publication policy shifted toward ﬁnal rather than in- terim publications. As a result only 15 papers were pub-

1 CL 1 -2 lished in 2001, compared to 27 in 2000. There were, as Observed ±1σ band usual, a large number of contributions to conferences, 10 e.g., 46 to the EPS Conference on High Energy Physics Background ±2σ band in Budapest, Hungary. The collaboration expects the analysis of the L3 data sample to last at least until the -3 a) end of 2003. 10 L3 At theend of 2000, 11 Ph.D. students in the Nether- 105 110 115 120 lands were analysing L3 data. NIKHEF physicists (in- m GeV cluding those from NIKHEF partners universities of Am- H sterdam and Nijmegen) contribute primarily to analy- 1 ses of the mass and couplings of the W-boson; QCD, b) in particular multiplicity correlations and Bose-Einstein correlations (BEC); two-fermion production, in particular τ pairs; searches for the Standard Model Higgs; -1 L3 ZZ production; charm and bottom production in two- 10 photon collisions; and studies of the cosmic ray muon s flux. Three Ph.D. theses were defended in 2001 on the Observed subjects of τ-pair production, resonance production in CL Background two-photon collisions, and the cosmic ray muon spec- -2 trum. 10 112.4 112.0 As in previous years, the computer farm in Nijmegen ±1σ band contributed a large fraction of the L3 Monte Carlo event ± σ production, accounting for more than 40 million events. -3 2 band 10 2.2 Searches 105 110 115 120 In theFall of 2000, the LEP experiments, in very pre- mH GeV liminary analyses seemed to have a small excess of events, suggesting the Higgs boson with a mass of Figure 2.1: (a) The background confidence level 1−CL around 115 GeV. The final analysis of the data was b and (b) the signal confidence level CL ,asafunction of therefore eagerly awaited. The final L3 analysis was s the Higgs mass hypothesis, m ,for all channels com- published in 2001 and gave a lower limit on the Higgs H bined. The solid line shows the observed value. The mass: m > 112 GeV at 95% confidence level. The H dashed line shows the median expected value in a large confidence levels as function of Higgs mass hypothesis number of simulated “background only” experiments. are shown in Fig. 2.1.

57 -1 preliminary preliminary 10 1 − − e+e →µ+µ (γ) L3 − − L3 0.9 e+e →τ+τ (γ) 0.8 fb A 0.7

0.6 ζ < o + −→ + − γ SM: 120 e e e e ( ) SM: ζ < 25o -2 10 0.5 1

Cross section (nb) 0.5 fb A

 √ > 0 SM: s« 75 GeV − −   e+e →µ+µ (γ) SM: √s« > 75 GeV SM: √s«/s > 0.85 + − + −  -3 e e →τ τ (γ) SM: √s«/s > 0.85 10 120 140 160 180 200 220 120 140 160 180 200 220 √s (GeV) √s (GeV)

Figure 2.2: Cross section as a function of centre-of- Figure 2.3: Forward-backward asymmetries as a func- mass energy for µ- and τ-pair production compared tion of centre-of-mass energy for e- µ-andτ-pair pro- with the predictions of the Standard Model. duction compared with the predictions of the Standard Model.

dard Model. Supersymmetric particles were searched 2.4 W physics forinmany different channels and kinematic regions. No signal was observed and in many channels limits cor- One of the main goals of the LEP programme is the responding to the allowed kinematic phase space were measurement of the properties of the W -boson. In established. Besides supersymmetric particles, searches totalsome 10000 e+e− → W +W − candidate events were performed for “exotic” leptons, e.g., “sequential,” have been selected. vector, and “mirror” leptons and heavy isosinglet neu- The measured cross section for e+e− → W +W − as a trinos. In all cases limits were set on their existence. √ function of s is found to agree well with the Standard 2.3 Fermion pairs Model, as do the branching fractions of the W . Apart fromthe lack of the Higgs boson, the Standard The differential production and decay cross sections of Model continues to agree well with the results from W -bosons, as well as their total production cross sec- LEP. An example is fermion pair production, where tion, are used in fits to determine the WWZ and WW γ cross sections and forward-backward asymmetries agree couplings. These results are combined with information well, as shown in Figures 2.2 and 2.3. These results on W couplings obtained from analyses of single W are used to place limits on several scenarios for “new production, ee → Weν,andsingle photon production, physics.” For example, the scale of quantum gravity ee → ννγ.Theself-coupling between the electroweak in theories with extra dimensions must be above about vector bosons in the WWZ and WW γ vertices plays 1TeV. acrucialrole in the gauge structure of the Standard

58 Model. Experimental tests of these couplings are sen- and the W + in a given event have been measured to sitive to new physics beyond the Standard Model. Pre- agree with the Standard Model prediction. liminary results find these couplings in agreement with The W mass and width are measured using a fit to the the Standard Model predictions and limits have been invariant mass spectrum of W decay products. Events set on anomalous contributions. are reconstructed into four jets (qqq¯ q¯ events), or two The cross section for the process e+e− → W +W −γ jets, a lepton (or τ “jet”) and a missing momentum has been measured for isolated, energetic photons in the vector identified with an undetected neutrino (qq¯ν detector. This channel is sensitive to quartic gauge cou- events). A kinematic fit is applied to the measured plings of the type WWZγ or WW γγ.Themeasured event, demanding energy- and momentum-conservation. cross section agrees with the Standard Model predic- The combined invariant mass spectrum is shown in tion, and limits have been set on anomalous contribu- Fig. 2.4. The W mass and width are extracted us- tions to these quartic couplings. ing an unbinned maximum likelihood fit by reweighting afully reconstructed Monte Carlo sample. These mea- From the joint decay angular distributions of W -pairs, surements are compared in Fig. 2.5 with the SM expec- the fractions of the different helicity states and their tation calculated using the world-average value of M . correlations are measured. W Good agreement is observed. CP conservation demands that the fraction of W − The dominant systematic uncertainty on the measure- bosons in a given helicity state be equal to the frac- ment of the W mass and width in the four-quark chan- tion of W + bosons in theoppositehelicity state. This nel arises from theoretical uncertainty on two QCD ef- has been verified experimentally and constitutes an- fects. One is the amount and nature of colour flow other test of the Standard Model. between gluons arising in the hadronisation of the qq¯ − In addition, correlations between the helicity of the W − from one W , e.g., W → du¯,andthosefrom the

preliminary preliminary 2.75 400 Data 172-208 GeV 2000 Data qqqq+qqlν L3 M.C. reweighted L3 M.C. incorrect pairing 2.5 300 M.C. background ] Best qqqq MW = 80.47 pairings ± 0.10 GeV 2.25 GeV

[ SM

200 W Γ 2

100 1.75 68 % CL Number of Events / 1 GeV Number of Events 95 % CL

0 80.2 80.4 80.6 60 70 80 90 100 M [GeV] [ ] W minv GeV Figure 2.5: The measured value of the mass and width Figure 2.4: The W -mass distribution, from which the of the W boson compared to the Standard Model ex- mass and width of the W boson are extracted. pectation.

59 1.3 2.5 QCD 0 0 L3 Data π π χ2 / ndof = 46.10/40 Stimulated by the need for better understanding of var- λ ± 1.2 Fit = 0.155 0.054 ious QCD eﬀects in order to reduce systematic uncer- Normalization R = 0.309±0.074 fm tainties on W -boson results, several investigations were 1.1 α = 0.021±0.034 pursued using the very high statistics Z-decay data pre-

(Q) viously (1989–1995) collected. 2 R 1 For the ﬁrst time in e+e− interactions, the BEC of neutral pions were compared to those of like-sign charged 0.9 pions. It was found (see Fig. 2.6) that the size of the source of neutral pions is somewhat smaller than that ± ± 0.8 of charged pions: R0/R±± = 0.67 0.16 0.15. 0.5 1 1.5 2 Also, the BEC among three identical charged pions is Q [GeV] being investigated. From the correlation functions for 1.3 genuine three-particle BEC and for two-particle BEC L3 π±π± χ2 Data / ndof = 42.55/40 one can investigate the degree of incoherence of the 1.2 Fit λ = 0.286±0.008 pion emission. Preliminary results found the data con- Normalization R = 0.459±0.010 fm sistent with completely incoherent production of the 1.1 α = 0.015±0.003 pions. Further, work continued on the investigation of

(Q) various parametrisationsofBECand on their imple- 2

R mentationinMonteCarloprogrammes. 1 2.6 L3+Cosmics 0.9 Understanding of the systematic uncertainties on the measurement of the cosmic ray muon spectrum and on 0.8 the charge ratio of this spectrum has increased consid- 0.5 1 1.5 2 erably. The final measurement is expected in 2002. Q [GeV] The analysis of the data from the air shower array on top of the L3 building is maturing. Combination of the Figure 2.6: The BEC correlation function R2 as function of the four-momentum difference between the pi- air shower array information with the number of muons ons for neutral and like-sign charged pions. The data observed in the L3 detector yields, through use of an are fitted to a Gaussian parametrisation. air shower simulation programme (CORSIKA), information on the primary cosmic ray composition. Very preliminary results suggest a larger amount of iron than previously thought. Asearchisbeing performed for an excess of muons in other W , e.g., W + → ¯sc.Thisisusually referred to the L3 detector which are correlated in time and direc- as colour reconnection. The other effect is BEC be- tion with gamma ray bursts observed by the BATSE tween identical bosons from different W bosons. satellite. Preliminary results show no excess of muons. Both of these effects have been intensely studied. Pre- liminary results have ruled out the most extreme models of these effects, indicating that the systematic uncertainties on the W measurements will be smaller than feared. Work is ongoing to reduce these uncertainties to the minimum. Another source of systematic uncertainty is the modelling of hadronisation in the Monte Carlo programmes, both in the hadronisation of W → qq¯ and in e+e− → qq¯,whichforms an important background to e+e− → W +W −.

60 CTheoretical Physics 1TheoreticalPhysics Group

1.1 Particles, fields and symmetries Higgs scalars in proton-proton collisions, a good understanding of this hadronic structure is a prerequisite. Theoretical physics provides the mathematical descrip- The precision of the experimental data requires QCD- tion of the properties and interactions of subatomic par- effects to be evaluated to a very high accuracy. Power- ticles. These include quarks and leptons (e.g. electrons ful techniques for computing QCD-effects to third or- and neutrinos), as well as field quanta like photons for der in the coupling constant α have been developed the electro-magnetic field, and gluons for the colour s at NIKHEF by Dr. J.A.M. Vermaseren and co-workers. field of the strong interactions. The electric forces bind Estimating the cross sections and rates for the produc- electrons to nuclei, whilst the colour forces are respon- tion of top-quarks and Higgs particles is part of the sible for keeping together the quarks inside the nucleon. research program of Prof. E. Laenen. These studies in- Furthermore the weak forces, mediated by heavy field clude analytic methods, like the resummation of large quanta known as massive vector bosons (W and Z), logarithmic contributions, as well as numerical simu- induce radioactive transmutations, notably the β-decay lations of certain types of events using Monte-Carlo of the neutron and the muon. methods. The general framework for the description of the sub- Anewinitiative has been taken to develop a set of atomic particles and their interactions is quantum field parton-distribution functions accurate to order α3 in theory. It provides a universal scheme for computations s perturbation theory, in which Prof. E. Laenen en Dr. of particle scattering and decay, for determining the J.A.M. Vermaseren cooperate with Dr. A. Vogt and properties of multi-particle and bound states, as well colleagues from experimental groups. as for studying collective phenomena such as symmetry breaking and phase transitions; an example of the Quarks and gluons at finite temperature latter is the transition from a hadron gas to a quark- In the collisions of heavy ions, such as lead on lead, gluon plasma expected to take place at extremely high at very high energies, the large number of particles in- temperatures. volved in the process allows for a thermodynamic treat- Present developments in quantum field theory relate to ment. There is good reason to believe that the energy increased understanding of the mathematical structures distribution over the different particles involved is of a involved, as well as to their application to the analysis thermal nature. The reaction times are very short com- and prediction of experimental results. In addition to pared to the duration of the ion-collision itself, allowing experiments at particle accelerators, the applications of equilibrium to be established. Therefore, one can as- quantum field theory and particle physics to cosmol- sign a well-defined temperature to the gas of hadrons, ogy and high-energy astrophysics is of increasing im- or possibly the plasma of quarks and gluons, which is portance. formed in the collision. Prof. J.H. Koch and co-workers 1.2 Research program study the effects of finite temperatures on the structure of hadrons. As a first step they have undertaken to de- The research program of the NIKHEF Theoretical Physics termine the temperature dependence of the form factor Group covers several aspects of quantum field theory, of the pion and the rho-meson. As also input from lat- string theory and their applications to the physics of tice gauge theory is required, they have initiated a col- subatomic particles. laboration with the university of Bielefeld (Germany), where the necessary expertise is available. QCD Supersymmetry The strong forces acting on particles with colour-charges, notably quarks and gluons, determine the structure of Supersymmetry relates the properties of bosons with hadrons. All of their interactions, including the electro- those of fermions. In field theories with an exact su- weak interactions, are affected by the hadronic environ- persymmetry the masses and charges of bosons and ment in which they live. To estimate reliably the cross fermions are equal. If supersymmetry is broken in a self- sections for production of particles like top quarks or consistent way, the masses of these particles may be-

61 come different although their charges remain the same. J.W. van Holten was responsible for the organisation Supersymmetric versions of the standard model exist, of the winterschool in theoretical high-energy physics but depend on a large number of free parameters. This of the Dutch Research School of Theoretical Physics number can be greatly reduced in the context of unifi- (DRSTP) in Nijmegen (January 2001). Prof. J.H. cation of the electro-weak and strong interactions. Koch participated in the organisation of the international Belgian-Dutch-German summerschool on exper- Non-standard scenarios for superunification are devel- imental high-energy physics in October 2001. oped at NIKHEF by Prof. J.W. van Holten and co- workers. Consistency conditions from quantum field theory have been incorporated, and allow for models with interesting phenomenological properties, including an explanation of charge quantisation. Superstring theory In string theory the point-like nature of elementary objects and field quanta is abandoned in favour of an extended object of finite length in one dimension. Point particles may be associated with such strings as viewed on scales much larger than the string length. However, more recently it has also become clear that one may associate point particles in a D-dimensional space with the endpoints of strings living in additional dimensions. These dimensions are not visible from the restricted D-dimensional space-time in which the end point of the string can move, although they may be probed by gravitational effects. This development has resulted in atheoryofD-branes, D-dimensional objects in which the end points of open strings can live. The notion of D-branes has become an important tool in elucidating non-perturbative effects in string theories. At NIKHEF Prof. A. Schellekens studies the interplay between such non-perturbative string dynamics and the perturbative dynamical behaviour of strings described by conformal field theories on their two-dimensional world surface. Gravity Gravity and cosmology have become intimately linked with particle physics. The behaviour of particles in strong gravitational backgrounds, such as black-hole or gravitational wave fields, is part of the research program of Prof. J.W. van Holten and co-workers. A recent new line of investigation in relativistic hydrodynamics and its supersymmetric generalisation has been opened up. 1.3 Teaching In addition to the research described above, the Theo- retical Physics Group is also involved in teaching, both in house and at the partner universities, and in the organisation of schools and conferences. In 2001 Dr. E. Laenen was appointed ordinary professor of theoretical physics at the university of Utrecht. Prof.

62 DTechnical Departments 1Computer Technology

1.1 Introduction The backup for the home and project directories on the Unix server ajax and the Windows-NT server paling has NIKHEF invested a total amount of 3.5 million NLG in been outsourced to the SARA ADMS backup services. the computer- and network infrastructure in the years During the nocturnal hours the data of the incremen- 2000 and 2001. A global idea on how this money was tal backups is transported through the WTCW campus spent is presented in figure 1.1. Apart from the up- network to the tape robot atSARA. By the end of the grades of the server and network infrastructure and the year 2001 the total amount of file storage on the robot replacement program for desktops, a major upgrade contained 1 TB of data. was performed of the hardware and software for the CAD workstations of the engineering groups of the elec- In thefourth quarter of 2001 a Xerox 2135 laser printer tronic and mechanical departments. Compute nodes was installed. and server systems were installed to increase the ca- 1.3 Network infrastructure pacity of farm resources for the LHC experiments. In the first quarter of this year an upgrade of the inter- misc. 7% nal local area network was realised. Stackable switches printers 2% desktops 13% with a port capacity of 100 Mb/sec and a gigabit uplink replaced switches with a port capacity of 10 Mb/sec. All desktop systems (with the exception of systems servers 11% connected to the guestnet)areconnected to the gigabit backbone with a 100 Mb/sec link. Most of the CAD 31% server systems are connected directly to the backbone through a link with a capacity of 1 Gb/sec. For this network 9% reason an additional blade with eight gigabit ports was installed in the backbone switch. This switch is the very same device as the hefrouter that connects the NIKHEF local area network to the outside world by farm 27% means of a 2 Gb/sec link to the WTCW campus network and a 1 Gb/sec link to our internet service provider SURFnet. SURFnet-5 became operational in October Figure 1.1: Computer investments 2001-2002 2001. SURFnet-5 offers a high-capacity connection to

Some examples of contributions from the CT engineering group will be presented below. 1.2 Central services In thecourse of the year 2001 essential services were migrated from the two Sun SPARCserver 1000 systems gandalf and park to the new server ajax.ThisSun Enterprise server 3500 is linked with a gigabit adapter to the network backbone and is configured with three RAID disk arrays with a total gross storage capacity of 1.2 TB. High quality file services are available for home and project directories. This file service provides NFS version-3 protocol to serve the Unix clients and CIFS protocol to serve Microsoft Windows clients. Miscel- laneous networks services, such as DNS, NIS, DHCP, RARP and Radius authentication for the dial-in server Figure 1.2: The network traffic between NIKHEF and were migrated to the ajax server. SURFnet during a typical period.

63 desktop system number remark imise the time spent on system installations. E.g. for Windows 175 including instrum- theinstallation of Windows-2000 one can install a ghost (98/NT/2000) entation systems image which includes not only the system itself, but Linux 150 excluding farm also some standard applications, such as Microsoft Of- systems fice. The aim is to develop scripts for the automation Other Unix 40 of system upgrades of Windows and Linux systems to (Sun, HP, SGI) decrease the effort spend on the maintenance of a large number of systems. Table 1.1: Overview of the number of desktop systems As a result of a market survey and extensive bench- for several operating systems. marking, the Sun Blade workstations were selected to replace the SGI and HP workstations of the engineering groups of respectively the mechanical and electronic departments. its users in the Netherlands and it operates a backbone with a capacity of 80 Gb/sec, a state of the art infra- 1.6 Farm configurations structure. Figure 1.2 presents the amount of network There is an increasing interest of our scientific users to traffic between NIKHEF and SURFnet for a typical pe- use stacks of standard PC’s, running some Linux ver- riod. sion and interconnected in a private segment of the net- To be able to offer more flexibility in case of meetings work. Sucha’farm’ consists of regular compute nodes and workshops and to overcome a shortage of fixed and server systems for management and file server pur- network connections on certain places in the NIKHEF poses. A farm consisting of 50 dual-processor DELL buildings, the basic components for a wireless network PC’swas setup in the year 2000 to generate Monte- infrastructure were installed. This service will be limited Carlo events for the D0 experiment. This year more to connect laptops to the guestnet segment of the local farms were installed to solve the computing needs of the area network. LHC experiments LHCb and ALICE and as a prototype for the ANTARES DAQ system. For a more sophis- 1.4 Security ticated use of this kind of compute and data storage Special attention was given this year to the protection resources, the European DataGrid project was started of the NIKHEF computers and services against haz- this year. In the second half of this year a number of ardous attacks from the internet. Given the facts that farm nodes and associated server systems were inte- the number of users and systems on the internet are grated into the DataGrid testbed-1 prototype. Other increasing rapidly and that our connectivity to the in- sets of nodes and servers were exported to the LHCb ternet is very good, it was not surprisingly to notice group at the VU in Amsterdam and the D0 group at that the number of attempts from non-authorised users the KUN in Nijmegen. to enter our network increased significantly. Measures For the new farms, we decided to configure and assem- were taken to prevent these attacks as much as possible rack-mountable PC’s ourselves. For this purpose ble. we selected the company JMS, specialised in building 1.5 Desktop systems rack-mounted PCs for industrial purposes. Once the requirements were established, the components were Table 1.1 presents a summary of the number of desk- ordered and built into a ’2-Units’ high chassis. A pho- top systems for each platform (no server systems in- tograph of the result is shown in Figure 1.3. Each node cluded). New systems installed run in most cases Mi- contains a dual-processor Pentium III processor with a crosoft Windows-NT / -2000 or Linux Red Hat ver- clock speed of 933 MHz, a gigabyte RAM, a 45 GB sion 6. Almost all new systems are commodity PC’s. hard disk and a 100 Mb/sec ethernet adapter. 3-Com Atotalof 110 new desktop systems were installed this switches with 24 ports each and a gigabit back plane year. Note thatthisisanaverage of more than two sys- interconnect the nodes. tems per week (excluding server and farm systems!). Remarkable is that about 40% of these systems con- 1.7 Amsterdam Internet Exchange (AMS- cerned new network connections, without trading in the IX) obsolete systems. NIKHEF is one of the four locations of the Amster- Procedures were simplified as much as possible, to min- dam Internet Exchange AMS-IX. This exchange is one

64 III LCM 1 LCM 2 LCM 3 LCM 1 LCM 2 LCM 3

PC 1 PC 2 PC 3 PC 1 PC 2 PC 3

LCM 1 LCM 2 LCM 3 LCM 1 LCM 2 LCM 3

Figure 1.3: Rack-mountable farm node

PC 1 PC 2 PC 3 PC 1 PC 2 PC 3

III IV of the largest exchanges in Europe in terms of number of customers (120) and the amount of network traffic (4 Gb/sec). The CT group is, in close collaboration with the technical facilities and financial departments Figure 1.4: Delayed transmission concept at NIKHEF, responsible for the infrastructure at the AMS-IX location. In spite of the decreasing invest- developed a delayed transmission method, which avoids ments in telecom market, we decided that an extension packet loss by balancing the traffic more evenly through of the location with another 60 racks could be justified. the network (Figure 1.4). This implied a major upgrade of the power and cooling infrastructure as well. The extension of the AMS-IX lo- 1.10 Embedded software for ATLAS hard- cation with 60 racks was ready to use for our customers ware modules in September 2001. In collaboration between hardware engineers from CERN 1.8 Software engineering and software engineers from NIKHEF a low-cost, low- power general-purpose microcontroller-based I/O-module The software engineering group participates in the Data- has been developed for the ATLAS experiment, called Grid project and in the ATLAS and ANTARES instru- ELMB (Embedded Local Monitor Board), see Figure 1.5. mentation projects. A selection of the software engi- As the name suggests it is a plug-on board that can neering contributions to the instrumentation projects is be embedded in other electronics systems. The ELMB presented in the following sections. has 64 analog inputs and 30 digital inputs/outputs and 1.9 ANTARES communicates to the outside world via a CAN field- bus. Two on-board 8-bit microcontrollers provide the In the ANTARES project standard industrial ethernet local intelligence. Components have been selected and components and network protocols were selected for the tested for better radiation-tolerance of the ELMB as a transport of the event data from the front-end systems whole. near the detector in the water to the on-line compute farms and data storage devices located in the shore In the ATLAS experiment a few thousand ELMBs will station. A prototype of this data acquisition system was be used for monitoring and control tasks throughout setup at NIKHEF for software development and system the detector. NIKHEF is one of the major users of the integration tests. To understand the behaviour of the ELMB (ca. 1200 modules) because it has developed a flow in the detector network, we performed a simulation monitoring subsystem for the ATLAS muon chambers study of the data traffic pattern. The results predict a based on the ELMB, so it took up the task of developing high level of packet loss due to repeated transmissions embedded softwareforthemuonsystemaswellasa from many sources to one destination. In response, we more general application.

65 Subscription DCSdata DAQdata Subscrition Commands DCSmessages Command results

DCS DAQ PVSS II Online DCC

DCSdata Subscription Alarms DAQdata Command Results Configuration Commands Database

Figure 1.6: DDC context diagram

communicate. The Trigger/DAQ DCS Communication (DDC) project should support the ability to:

• exchange data between Trigger/DAQ and DCS; Figure 1.5: Apictureof the Embedded Local Moni- tor Board (ELMB).AnI/Omodule developed for the • send alarm messages from DCS to Trigger/DAQ; ATLAS experiment. • issue commands to DCS from Trigger/DAQ.

Each subsystem is developed and implemented indepen- Although the various users of the ELMB often have dently using a common software infrastructure. Among different requirements, many aspects in the embed- the various subsystems of the ATLAS Trigger/DAQ the ded software of the ELMB are incommon, such as Online is responsible for the control and configuration. the communication functions for the CAN-bus using It is the glue connecting the different systems such as the CANopen protocol, the in-system-programmability data flow, level 1 and high-level triggers. The DDC uses (the ELMB can be reprogrammed in-situ via the CAN- the various Online components as an interface point on bus), the automatic health-checks, configuration stor- the Trigger/DAQ side with the PVSS II SCADA system age, etc. Special precautions have been built into the on the DCS side and addresses issues such as partition- software to better withstand radiation effects (mem- ing, time stamps, event numbers, hierarchy, authoriza- ory bit-flips), which otherwise easily crash a running tion and security. PVSS II is a commercial product cho- program. The second onboard microcontroller has the sen by CERN tobetheSCADAsystemforallLHC ex- important task of detecting such events (they still hap- periments. Its API provides full access to its database, pen) and taking appropriate action. which is sufficient to implement the 3 subsystems of the NIKHEF has provided a fully operational general-purpose DDC software. The DDC project adopted the Online application program for the ELMB (for both microcon- Software Process, which recommends a basic software trollers) which can be used as-is, but users are free to life-cycle: problem statement, analysis, design, imple- change and add to this software, since the source code mentation and testing. Each phase results in a corre- has been provided, as well as documentation. A few sponding document or in the case of the implementa- hundred ELMBs have produced so far and they are in tion and testing, a piece of code. Inspection and review use by several people in different test set-ups, not only take a major role in the Online software process. The by ATLAS, but also by severalotherexperiments and DDC documents have been inspected to detect flaws CERN groups. A production series of 7000 is currently and resulted inaimprovedquality.Afirstprototype of being prepared. The embedded software for the ELMB the DDC was ready and used in a test-beam set-up dur- is being refined and extended. ing summer 2001. Figure 1.6 shows the basic context 1.11 Communication between Trigger/ DAQ diagram of the DDC package. and DCS in ATLAS 1.12 Applications for the production of ATLAS muon chambers Within the ATLAS experiment, the Trigger/DAQ and DCS (Detector Control System) are both logically and During the production of drift tubes for the muon physically separated. Nevertheless there is a need to chambers, many checks are performed to guarantee

66 high mechanical precision. These checks, involving quantities such as temperature and wire tension, are automated andimplemented as LABVIEW applications using the CAN ﬁeld bus as hardware interface. Also, asetuptomeasure, for 80 drift tubes simultaneously, the gas leak tighthness and the High Voltage behaviour over a period of several hours, was completely automated. Most notably is the LABVIEW application that steers the gluing ’robot’. This machine is used to glue layers of 72 tubes laying on a granite table (2.5m × 5m) to atubelayeralready on the muon chamber. The programme controls the various step-motors that move the machine and its gluing units and distribute the glue. Af- ter the operator has selected the appropriate operation via a graphical user interface, the process is started automatically and is continuously monitored by the software.

67 Cabling at the Amsterdam Internet Exchange.

68 2Electronics Technology 2.1 Introduction 2.2 Projects The work carried out by the Electronics Technology 2.2.1 HERMES Group in 2001 was focused on three main subjects: To protect the Lambda Wheels against unnecessary radiation damage caused by unstable beam conditions, a • Finalizing the components for and the installation Beam Loss Monitor (BLM) was developed, tested and of the Zeus microvector detector and the Hermes installed in the shutdown period of the HERA beam. lambda-wheel detector. These detectors will be- The BLM consists of two sets of four ionization cham- come operational in 2002. bers,placed at a distance of 20 cm from the beam in • Designing components and start prototype pro- the horizontal plane. duction for the LHC detectors at the Atlas, LHCb In case of too high radiation levels, the BLM gener- and Alice projects. For this prototyping the group ates a trigger signal, which is sent to the dump kicker. provides support with high standard instrumen- Each ionization chamber is equipped with a charge sentation like signal analysers, oscilloscopes, power sitive preamplifier with a shaping time of 5 µs, and a meters, SMD (Surface Mounting Devices), han- line driver. Three of the four chambers monitor the dling tools, etc. radiation level, while the fourth dummy chamber supplies a veto signal in case of electromagnetic pickup. • Components for other non-accelerator based proj- Adiscriminator unit that filters spurious signals picked ects like Antares and Medipix. up during transmission handles the analog signals from the front ends. The major trigger decision is built in Because of this large number of projects there is a per- standard NIM logic. For diagnostic purposes, a PC- manent high claim on the manpower (staff of 35 fte) based ADC card records the front-end signals in a time and expertise of the group. In Fig. 2.1 the projects are window around the trigger. listed that consumed ≥ 0.5 fte. 2.2.2 ATLAS Monitored Drift Tubes (MDT) On the MDT production site the department provides support by optimizing the controls and installing several fte 0123456 extra test features. This site has to produce 96 of the

Zeus largest muon chambers of the ATLAS detector. projects Hermes For the MDT chamber tests a cosmic-ray setup has Atlas-MDT been realised. A signal-delay line of ≈11 ns has been

Atlas-DAQ developed that is made of a four-layer PCB with a high voltage isolation of 4 kV. Atlas-DCS

Atlas-diverse With this delay line it becomes possible to measure

LHCb-outertracker the z-coordinate with higher accuracy. The advantages of this delay-line construction are a low price by mass LHCb-vertex production, a high reproducibility, and the absence of LHCb-pileup magnetic parts. Alice Semi-Conductor Tracker (SCT) Antares

New Projects Prototype SCT silicon detector modules have been extensively tested. The modules are functional, but under NIKHEF certain conditions they show instabilities. Due to the Internal small size of the components and sophisticated functionality, debugging is a real challenge. Diﬀerent groups within the ATLAS collaboration are working on the sta- Figure 2.1: ET manpower distribution in 2001

69 Figure 2.2: Delay line for MDT test purposes. Dimen- sions in mm are 51×26×3.5, weight is 9.1 g. Figure 2.3: The MROD-1 module with at the left three S-link daughter boards and in the centre two of three MROD-in boards. On the right are the three VME64x connectors. bility problem. At NIKHEF it has been shown that noise entering the power distribution from the digital logic was a source of the instability. Better decoupling tween CPU, grabber and four Rasmuxes were built for of the power distribution was required. The biggest the chamber production sites. problem was finding space for the surface mount components. There was no space on the kapton hybrid, The specifications for the cable types, lengths and con- and designing a new four-layer kapton circuit would be nectors for all chamber components were finalised. too time consuming and expensive. To test some pro- With the low-cost RasNik components a test setup for posed improvements we used a small (5 mm x 6 mm) LHC magnet alignment was installed at CERN. kapton circuit that was glued directly on the active part of the ABCD Integrated Circuit. The mini-kapton has Muon Readout Driver (MROD) asinglecopper layer with electrical connections to the The design and simulations of the MROD-1 prototype chip made by wire bonding. Modification of a module were finished. This prototype will support six input with short silicon wafers at NIKHEF was very success- links, from a Chamber Service Module (CSM) on the ful, resulting in the first stable short-wafer module. The Muon-chamber. The CSM converts serial data-bits same recipe was tried on a long silicon-wafer module. from at maximum 18 TDC’s ofonelayeroftheMuon- It considerably reduced the instabilities but, unfortu- chamber into 32-bits data words. The MROD groups nately, failed to cure them. More work is needed to these data words for each TDC and checks whether solve this problem, including the development of a new the data from all TDC’s belonging to the same event six-layerhybrid. number have arrived. The data from this event are RasNik Alignment system formated and sent via an output link to the Read Out Buffer (ROB) for further processing by the central Data The full series production of 5700 RasCaM’s (sensor) Acquisition (DAQ) system. The use of Digital Signal and 6300 RasLeD’s (light source) modules was finished. Processors (DSP’s) makes extensive error checking, re- Apre-production of RasMuX (multiplexer) modules was covering and self-testing possible. carried out. Here, the mechanical envelope was optimised such that it will fit on (almost) all chambers. The MROD-1 consists of a 9U x 400mm VME64x Radiation hardness tests were continued, resulting in board, called MROD-out, on which three daughter the conclusion that some replacement of components boards, called MROD-in, are mounted. Furthermore six is needed. Temporary interface boxes (MiniMaster) be- S-Link Destination Cards (LDC) and one S-Link Source

70 Card (LSC) are also mounted on the MROD-out. All Assistance was given with the further development of S-Links operate at a speed of 160 MBytes/s. Each the straw chamber in the area of chamber boards, MROD-in accepts and organises the data from two S- grounding and shielding and beam tests at CERN. Link inputs. The MROD-out collects and formats the Aprototypeboard for measurement of very low currents data from the three MROD-in boards and sends its data in the high-voltage lead of a straw has been developed; to the Read Out Buffer via the S-Link output. Further- it is able to measure currents down to 100 pA. more the MROD-out communicates with the rest of the system via a Timing, Trigger and Control (TTC) Together with our colleagues from Krakow we have suc- interface and via a VME64x interface. cessfully tested a digital front-end prototype for the Outer Tracker in November as a proof of concept. After Two MROD-in boards and one MROD-out board are further developments it can serve as a backup solution. produced at the moment and tests were started. The The next step will be the development of a special Time test-setup is built up with a prototype of the standard to Digital Converter (TDC) chip at Heidelberg and the ATLAS 9U-VME64x crate. matching front-end electronics by NIKHEF. Addition- During testing minor were problems discovered in the ally we have provided a Timing and Trigger Control design of the MROD-1 which were easy to fix by (TTC) generator and receiver to trigger our present re-programming theField-Programmable Gate Arrays and future front ends in a CERN-compatible way (on (FPGA). However, a serious problem with the SHARC glass fibre). Digital Signal Processors (DSP) showed up. Depend- LHCb Vertex ing on the skew between the power-on sequence of the 3V3 and 2V5 power inputs of the SHARC DSP’s, the In order to design reliable mechanics for the Vertex de- internal Phase-Lock Loop (PLL) circuit can get locked tector investigations were done to characterise its high- in an error state, preventing any further use of the DSP. frequency behaviour. A(difficult to implement) hardware patch of the power distribution in the MROD-1 will have to be realised to To measure the longitudinal coupling impedance of solve this problem. The MROD-1 interfaces to the TTC the Vertex mechanical setup under realistic conditions system via a TTC Interface Module (TIM) that is devel- ameasurementtank (mockup tank) has been con- oped by the University College London in the UK. The structed. This tank has been built up according to TIM needs a special P3 backplane in the VME64x crate. the latest design review in which all parts like silicon This backplane is developed by the Royal Holloway Uni- detector boxes and bellows are simulated by aluminium versity of London, also in the UK. A prototype of the and stainless steel parts. In the final design the silicon TIM module and a backplane are integrated in the test- detector boxes have to be movable from closed position setup of the MROD-1. After a few start-up problems, to a maximum opening of 60 mm, which is desired for the TIM was working correctly with the MROD-1. the beam-injection cycle. Besides functioning as a Muon Read-Out Driver, the The connection of the LHC standard beam pipe of hardware of the MROD can also be used to build a 54 mm to the 12 mm inside dimension of the boxes is Read-Out Buffer. Exactly the same hardware that provided by the so called ‘Wakefield suppressors’ (see forms the MROD-1 can be transformed into a ROB, Fig. 2.4), mounted at both sides of the boxes. The only by re-programming the functionality in the FPGA’s. goal is an ‘ideal situation’ (beam pipe with right di- During the design of the MROD-1, the possibility for mensions and the change by means of closed tapers), the transformation to a ROB was taken into account. with no coupling to the tank and where the real part ≈ The re-programming of the FPGA’s and testing of the of the impedance is 100 Ω.Themeasurement results ROB functionality is planned for the near future. are still < 100 Ω for the boxes closedoratadistance of 20 mm of each other. At silicon box distances from 2.2.3 B-Physics 20 to 60 mm the opening in the wake field suppressors produces an increase in RF coupling to the tank res- LHCb OuterTracker onances and the real part of the coupling impedance Most of the work done was focused on the Technical increases to 400 Ω.Tominimise this RF coupling a Design Report, published in September 2001. Assis- modified wake field suppressor will be constructed. tance was given in the form of specifications and pre- Ameasurement was performed close to the shielding designs of the electronics. The work also resulted in of the silicon detector boxes. EM field penetration two public LHCb notes.

71 in Heidelberg, Oxford University and NIKHEF various components of the front-end chip have been submitted in the 0.25 µmCMOStechnology and tested. During this year we characterised a prototype front-end and discriminator chip before and after irradiation. Also two completeBEETLE 1.1 chips were connected to a silicon strip detector and successfully operated in a test beam at CERN. Apointof concern is the cabling inside the vacuum tank of the vertex locator. Apart from the radiation and out-gassing requirements, it should be able to withstand 10000 movements during its lifetime. The basic solution is a fine-pitch strip line on a kapton backing. 2.2.4 ALICE For the ALICE programme NIKHEF designs the elec- Figure 2.4: RF suppressors at the detector box of the tronics that handles the signals between the front-end LHCb Vertex detector tank. hybrids in the Silicon Strip Detector (SSD) and the data acquisition outside the detector. This electronics is placed at both ends of each detector ladder and through the thin aluminium shielding of the boxes pos- is called an EndCap module. The development of the sibly increases the noise level of the output signal. electronics was presented at the 7th WorkshoponElec- tronics for LHC Experiments,heldinStockholm. Acoaxialline of 50 Ω has been made of which the outer conductor consists of aluminium foil, the thickness of The electronics must be radiation tolerant and there- which can be chosen. The power level in this coaxial fore application specific IC’s (ASICs) are being devel- line over the frequency band of interest, in our case oped using 0.25 µmCMOStechnology. Two types with an upper limit of 150 MHz, can be increased to of ASICs are necessary, a control and buffer ASIC for 15 W maximum. In this way the EM field level at the all signals that are needed for the front-end chip on outside of the foil can be controlled to the expected the detectors (ALCAPONE) and an analog buffer to level introduced by the beam in the desired frequency send the analog data from the detector to the data- domain. acquisition (ALABUF). In the design of the EndCap module, power consumption, mass and space are im- At 0.5 mm distanceofthealuminium foil a proto- portant issues. Low power ASICs reduce the amount of type silicon detector with a BEETLE front end will be space and power in comparison with several commercial mounted. IC’s that would be needed instead. LHCb Pile-up Veto system Three prototypes of parts of the complete ASICs have For the Pile-up Veto project a full-scale prototype of been designed (see Fig. 2.5), produced and (two) tested the vertex processor was designed and currently the in 2001. One of the tested circuits is a radiation- printed circuit board is being developed. The central tolerant power-supply regulator and the other is an ana- part of this board consists of two large FPGA’s with log buffer with multiplexer for the handling of the ana- 3.2M logic gates each. These FPGA’s contain the cor- log detector data. After the tests these parts will be relation matrices that produce the trigger decision as integrated in the complete control chip which will be input for the level0 trigger logic. produced early 2002. The Pile-up Veto system supplies a trigger decision to The control chip has functions for buffering digital the level0 trigger of LHCb. Therefore, digital data are (LVDS and CMOS) signals, for the control of config- required prior to level0 buffering. The only readout uration data of the front-end chip and the chip itself, chip for strip detectors that can deliver these discrimi- for power regulation of the power in the EndCap and nated signals is the ‘BEETLE’ chip. It was therefore de- the front-end Hybrid. This makes this ASIC a ‘mixed- cided to increase the effort in the development and test signal’ design with analog and digital functions. Both of this chip. In a collaboration between the ASIC-lab the analogue- and digital parts are verified with sim-

72 Figure 2.6: Powersupply part to feed two of the six sectors (2×180W-400V) in a string. Figure 2.5: Prototype ASIC in test package.

ity of the Avalanche Photo Diode (APD) circuit of the ulations. The digital part is designed using Verilog as optical receiver asked for expertise in the field of high the description language. The layout is generated auto- frequency and cooling. matically, whereas for the analog part everything must be done by hand. In order to increase the NIKHEF expertise on optical networks several industrial courses were attended by ET 2.2.5 ANTARES personnel. During the year 2001 the final Technical Design Report Power distribution has been completed and construction of the first string components has been started. Deployment of one sec- Based on the proposed power distribution from the 1 tor, a modular unit corresponding to 6 of a string, is conceptual design report the string power distribution foreseen for 2002. NIKHEF contributes to several parts topology has been designed. It will exist of two parts; of this project. astringpowermodule and a local power box. The string power module will convert the power from shore Optical network to a dc power such as to minimise noise and optimise For the communication between shore and detector efficiency (see Fig. 2.6). This power will be converted parts an optical network will be applied. This system by the local power box in each module into all voltage will be based on dense wavelength division multiplexing levels needed by the different electronic boards. A pro- (DWDM) at 1500 nm - 8 wavelengths on ITU-grid at totype of the SPM has been realised by the firm Power 400 GHz separation. Concept, specialised in power supplies and reliability. The final optical DWDM network design for Antares Module mechanics was concluded with the continued cooperation of the fi- The original module crate setup designed by the project bre optics engineering firm Coenecoop. DWDM lasers, partner in Marseille has been evaluated. The tempera- DWDM receivers and DWDM multiplexer-filters were ture behaviour of all boards has been taken into account selected, with emphasis on extreme long-term stability to produce a concept that can dissipate all power in a for unattended underwater operation for over 10 years. reliable way. An improved design, which was presented Details in fibre handling, connecting and routing inside to and accepted by the collaboration, served as a ba- the electronic crates and titanium cylinders were fixed. sis for a prototype (see Fig. 2.7), which will be tested NIKHEF has investigated lay-out issues, such as high- at the beginning of 2002. A grounding and shielding frequency constraints, ground loops, shielding and tem- philosophy was also included in this design. perature behaviour of the DWDM board. Especially the Test system setups 2.5 GHz transmit laser and laser driver circuit, with its high current 80 ps rise-time edges and the V sensitiv- Special equipment to test the parameters of optical net-

73 SCM, have been tested to a pressure of 300 bar at the IFREMER Brest high-pressure test facility. A delay vari- ation of -10 ps/bar/km and a negligible attenuation as function of pressure have been measured. Optical loss measurements have been made at the tension tests of the vertical string cable in Marseilles. Without tension, the cable showed a larger loss than specified and the loss increased dramatically at higher tension. 2.2.6 Medipix An interface was developed and tested successfully in 2000. This year new designs for interfacing electronics and pixel carriers have been provided for the new larger and faster Medipix chips. NIKHEF contributed to two challenging aspects: to realise a 200 MHz read-out system for the chips and to realise a printed circuit board with a very high resolution as carrier for the pixel chips. Early 2002 the test phase will start. 2.3 Department development As the Electronic Technology Group is involved in a wide variety of projects, a broad field of expertise and high-quality tools are a prerequisite. To keep the expertise on the required level and to increase the deployabil- ity of the members of the electronic department various courses were attended by members of the group. For Figure 2.7: Test system for temperature behaviour of instance, knowledge about electromagnetic compatibil- the electronics. Diameter 155 mm, height 420 mm, ity is very important for the high-frequency designs of weight 9 kg. communication electronics and electronics in a noisy environment, especially for near-beam experiments and when switching power is close to the electronic circuits. work systems was required. Wavelength precision and Other fields in which expertise is required are VLSI- stability, damping and reflection, and bit-error rate de- design, PCB-design and optical networks. tection are important items to check before installa- Due to the specific electronic constraints on printed cir- tion of the network. Crucial instruments were selected cuit boards, the layout of most of the boards is done and acquired, such as an Optical Spectrum Analyser, a in house. This means a high claim on expertise and Tunable 1550 nm Laser Source, an Optical/Electrical tools. Presently two layout systems are in use. The converter, etc. Also, a real-time oscilloscope with high software of the Ultiboard system has been upgraded. analog bandwidth (> 2.5 GHz), high sampling rate (20 Many special features have been realised in intensive GHz) and matching 4 GHz active probes has been se- contacts with the supplier. For the Mentor Graphic sys- lected for electrical test probing and verification of the tem new workstations and software with new features, DWDM circuitdesigns. like a state-of-the-art autorouter, have been installed. Several tests on optical connections were performed The ergonomic aspects of the office furniture and the as a proof of concept. A 50 km optical-link test was workshop furniture are being evaluated on a continuous carried out. To interface the commercial single-mode basis. Half of the almost 40 years old furniture has transmitter and receiver to the Gigabit Ethernet cards, been replaced with modern parts. The new desks are two 1000base-SX to electrical signal converters with re- in accordance with the latest ergonomic (e.g. RSI) and timer where built. Without optimalisation a Bit Error safety (ESD) regulations. Rate < 3 × 1011 was measured. The optical fibres of the Interconnecting cable, between Junction Box and

74 3Mechanical Workshop 3.1 Introduction The mechanical workshop has contributed to several projects. The work varied fromconstructingprototypes to the serial production of muon chambers, which is presently the largest project. Below the contributions are described in more detail, ordered by invested manpower. 3.2 Projects 3.2.1 ATLAS Muon chambers (7.4 Fte) After a period of preparation, the serial production of 96 ATLAS muon drift tube (MDT) chambers started in June 2001. An MDT chamber consists of 2x3 tube layers glued on a support structure with high precision (aim: < 20 µm). Each layer consists of 72 drift tubes. Figure 3.1: Some of the ATLAS Muon chambers and The production line starts with the assembly of pre- storage racks produced in 2001. In the background the cision end-plugs, which hold the wire in the centre of MDT (cosmic Ray) test station. the drift tubes. The drift tubes are then finalised with asemi-automated wiring machine, which successfully wired about 4000 tubes. During the production pro- Four chambers, which were produced in 2001 were sent cess, experience was acquired by the operator, which to CERN to undergo an X-tomography scan to deter- allowed to make improvements to this machine. mine the position of each of the 432 wires. The results As part of the standard Quality Control procedure, all are excellent: all four chambers have their wires posi- produced tubes are checked by measuring the wire ten- tioned to typically 15 µmRMS. sion, leak rate and High Voltage behaviour. About 10% In thefall of 2001 we have set up a test station for of the tubes are also checked by measuring the wire po- MDT chambers using cosmic muons, see Fig. 3.1. This sition which is determined by two precision end-plugs. station allows testing all the chambers before they are The final rejection rate is about 2%. stored (to be installed in 2004 in ATLAS). The first step in the chamber assembly is the construc- For the coming years the production of muon chambers tion of the support structure (spacer), which takes in will continue; we are studying production schemes that the present set-up at least 2 days. Then, in six sub- allow us to produce chambers in a 7 working day cycle. sequent days, the tube layers are glued to the spacer. Each gluing step is prepared carefully to ensure that 3.2.2 ATLAS Semi-Conductor tracker (2.5 Fte) only good quality tubes are used and that each tube is We tried several techniques to find the best way to ma- placed in the gluing jigs to high accuracy. The gluing chine the carbon fibre discs, used as support structures machine, used for gluing the tube layers, is now oper- of the tracker. During these studies we obtained ex- ating with disposable glue-cylinders, reducing cleaning perience and found that it is necessary to use a mould time. In addition a glue mixing and dispensing ma- to retain the disc while milling. The first tests for se- chine has been bought to avoid hand mixing. A total rial production were made with a 1/3 pie piece of a of eight chambers were produced in 2001. The first full size disc, see Fig. 3.2. We adopted the following chamber took 18 days to build, for the last one in this procedure. First, the holes are machined. Then, the year we needed 8 days. mounting blocks, inserts and pads are bonded onto the Some chambers are equipped with gas systems. The disc. Finally, it is machined to the required height and production of the required parts has started and in the flatness. future we foresee to equip all chambers with gas sys- ACarbonfibre (Korex) core, which will probably be tems directly after assembly. used in the future, is very sensitive to moisture. For this

75 Figure 3.3: The stainless steel parts of the safety valve before welding.

Figure 3.2: Prototype piece for a full size disc with mounting blocks and other inserts. bellows are being made. The movements have to be followed by the Wakefield suppressor. A few models of Wakefield suppressors were made this year. The best reason we made a prototype storage- and transport box, design was chosen and fatigue tests will follow in 2002. which can be flushed with a dry gas. The electronic 3.2.4 LHCb Outer Tracker (on average 2.2 Fte’s) design of the silicon modules (K4) has not yet been finalised, which prevents the further development of the We performed much prototype work for the wire loca- mechanics concerning these modules. However, various tors and the tools needed for production of the straw precision prototypes for cooling- and module support chambers, see Fig. 3.4. The way of putting a wire in are already being made. atubeistosuck it through using an air pump and/or to blow it through with compressed air. Despite sev- 3.2.3 LHCb Vertex detector (2.6 Fte) eral attempts to automate the wiring of the tubes and We constructed a prototype thin-walled foil, which is putting the locators in place, the wiring by ’hand’ seems used to separate the silicon modules from the primary to be the best option to get the 50.000 tubes wired. vacuum. The foil can be produced ’cold’ with a pressure At NIKHEF we decided to wire the tube by using the of approximately 65 bar or ’warm’ (500 Celsius) with a suction method, in combination with soldering a little pressure of approximately 15 bar. Initially, the thickness of the foil is 250 µm. At places where the foil needs to be bent to follow the shapes of the silicon modules its thickness is reduced to only 70 µm, which has led to several leaks. We are confident that these leaks can be avoided in the future. The silicon modules are placed in a secondary vacuum vessel, which is connected to a safety-valve to protect the thin separation foil against high pressure differences (limitation at 3 mbar.). This valve was designed and made at NIKHEF. Figure 3.3 shows the parts of the valve before welding. The valve was tested and the results are promising. During data taking the detectors have to be positioned at 8 mm from the beam, but until stable beam conditions are reached, they have to be retracted over 3 cm. For this movement, a bellow on each side of the Figure 3.4: Prototype of a LHCb Outer Tracker cham- beampipe will be used. The first prototypes of these ber.

76 ment delivered in the past to ESRF in Grenoble. A new prototype slit has been successfully constructed and the green light was given to produce twelve ﬁnal slits. 3.2.10 ALICE (on average 0.2 Fte) In collaboration with the University of Utrecht we contributed to prototype work for the ALICE detector.

Figure 3.5: CO2 evaporator cooling circuit AMS. bullet of tin at the end of the wire, to be cut off at the end of the wiring. Another issue to work out was the electrical contact between the straw and the honeycomb material covered with conductive foil. The latest suggestion is to make a lip at the end of the straw and clamp it withametal plate to the contact. 3.2.5 ZEUS micro vertex detector (on average 1 Fte) In February the pre-assembly and tests of the two detector halves took place at DESY. In May, the detector was successfully installed in the ZEUS experiment. 3.2.6 HERMES (on average 0.8 Fte) Allsilicon modules were bonded and tested. A system to mount the modules in a precise way on the ’lamba wheels’ was constructed. The mounting scheme was successfully tested at DESY. The final assembly will be,after some delay, realised in March 2002. 3.2.7 ANTARES (on average 0.5 Fte) For Antares we made prototypes of the crates that will hold and cool the p.c. boards. Some crates were made for testing in awater container, some for the test string in the sea. 3.2.8 AMS (on average 0.4 Fte) The first prototype of an AMS cooling ring (Fig 3.5), including mounting pieces, has been made. 3.2.9 DUBBLE (on average 0.4 Fte) The group took care of service aspects of the equip-

77 The cosmic ray test stand at NIKHEF with four BOL chambers installed.

78 4Mechanical Engineering 4.1 Introduction The Engineering Group has been involved in many projects in the development phase in the year 2001 as shown in Fig. 4.1. Moreover the group invested manpower in projects in the running phase, projects for third parties and the internal operation of the group.

3 Fte

2 Figure 4.2: Installation of the Zeus micro vertex detector

0 −9 LEP Zeus Hermes ATLAS ATLAS ATLAS ATLAS LHCb LHCb Alice Antares Dubble AMS construction materials appeared to be 10 mbarl/sec. ECT MDT SCT D0 OT Vertex bedr. The development of the toolinginordertooptimise the production site was a major investment for our group. Figure 4.1: Distribution of manpower of the Engineer- 4.3.2 ATLAS SCT ing Group in 2001 over the projects. The final design of the discs is depending on many pa- 4.2 Running Experiments rameters like cooling, minimal mass, and stiffness and alignment aspects. The fixation of the disc in the cylin- 4.2.1 HERMES der with respect to the vibration modes, resulted into the design of a flexible fixation. The optimization of Afinal test installation of the silicon detectors and their the number of fixations with respect to the resonance cooling system has been performed. The final integra- frequency of the assembled disc has resulted in a feasi- tion on the lambda wheels is waiting for the test runs ble solution, see Fig. 4.3. A lot of effort was put into of HERA in order not to risk damaging the detectors. the final specifications for the outsourcing of the disc 4.2.2 ZEUS manufacturing where a balance between quality control and costs was found. In a fruitful collaboration with colleagues from Oxford University the micro vertex detector has been installed Astorage box for discs equipped with silicon modules, in the beginning of 2000 in ZEUS (Fig. 4.2). All pre- cooling systems and electronics in a protective atmo- cautions with respect to damaging the silicon wafers sphere has been designed and built such that a protec- have been effective. The preliminary tests with cosmic tive gas atmosphere could be created. rays show a perfect behavior of the detector. Afiniteelement study has been performed in order to 4.3 Projects in development predict the influences of temperature changes of the cooling circuit on the stability of the disc. 4.3.1 ATLAS muon chambers 4.3.3 LHCb Outer tracker Major progress has been made in finalizing the production drawings of the muon chambers of the ATLAS The final prototypes have been designed and tested detector. The leak tightness of the tubes has been at CERN and at DESY. Discussions with the Heidel- checked in an automated test setup. Diffusion of the berg group are still ongoing with respect to the electri- helium test gas through the sealing complicates the pro- cal properties of the assembly. Grounding problems in cedure considerably, as the diffusion rate for the chosen combination with conductivity of the straws have been

79 been designed and constructed. Integration and testing of this crucial construction still is ongoing. 4.3.5 ALICE The design of the silicon strip modules for the Inner Tracker Silicon detector (ITS) was finalised. Special tools for its construction and handling are being designed in collaboration with Utrecht University. For the mounting of these modules on the carbon fiber ladders we designed an innovative, high precision, assembly robot, see Fig. 4.4. The construction is partly performed at Utrecht University and partly in industry, under supervision of NIKHEF. Possible corrosion in the thin (40 µm) walled cooling tubes for the modules requires a thorough study by the engineering group. Many integration issues are still to be decided upon by the collaboration. We play an important role in the Figure 4.3: The figures show the relative deformation ongoing discussions. as an effect of the vibration in the first and second resonance frequency respectively.

solved in the design. The test setup for this construction will lead to the final decision. The design of the production site has evolved to a final setup. The tooling design is in full progress. Afiniteelement study has been carried out in order to determine the stiffness of the modules, which consists of an assembly of the detection straws and their supporting panels. Different types of wire locators were made by rapid prototyping to test their performance in the wire insertion process. This evolution of prototypes resulted in a final version made by injection molding suitable for mass production. Figure 4.4: Positioning mechanism for the ALICE silicon detectors. 4.3.4 LHCb Vertex detector The prototyping of the various challenging items in the 4.3.6 ANTARES construction of the equipment in the vertex region has Thermal simulation studies of the MLCM1 and SCM2 evolved, e.g. the so-called gravity valve. The protection electronics crates were performed to come up with a of the primary vacuum against back streaming from the crate design with a good thermal contact between the secondary housing can by this mechanism be guaran- DWDM3 laser board and the 14 o Cseawater.This −9 teed to a level of less than 10 mbarl/sec. Progress good thermal contact is necessary to minimise the has been made on the manufacturing of the ’toblerone’ power consumption of the Peltier element, which is shaped 250 µmaluminum foil. The adjustment mech- used to control the temperature of the DWDM Laser. anism for the alignment to the beam centerline and the Aprototypecrate was made and tested successfully in cable routing have been finalised in the design. Many presentations of NIKHEF experts at CERN gave the LHC committees the confidence in the present design. 1. MLCM: Master Local Control Module 2. SCM: String Control Module The parts for the realization of the large bellows have 3. DWDM: Dense Wavelength Division Multiplexing

80 awater container simulating the deep sea water conditions, see Fig. 2.7 in Chapter D2 on page 74. 4.3.7 ATLAS end cap The first vacuum vessel has been leak checked at Ex- otech in Vlissingen. We assisted in doing this quality control. After transportation the vessel had to be integrated and tested again at CERN. Just before Christ- mas this job was successfully finished. 4.3.8 AMS Our group also contributes to the thermal study of the tracker in the Alpha Magnetic Spectrometer. A prototype of an innovative space compatible cooling system based on CO2 cooling liquid has shown an almost ideal behavior. The specifications of the total system are fixed and we will start building the final circuit in collaboration with the Dutch Aerospace Laboratory (NLR). 4.3.9 DUBBLE Aredesign of the slit construction in the beam line has been performed. The parts are under construction. Several set ups for the experimental stations have been produced. 4.3.10 COLDEX Measurements of ion desorption effects in a temperature trajectory of 2K to 30 K are ongoing. The apparatus that we have designed, built and tested is at present being implemented in the SPS machine at CERN, producing data with which the conditions in the future accelerator can be simulated. The quality of the LHC vacuum is among other effects depending on these figures.

81 The D0-farm at NIKHEF.

82 5GridProjects

5.1 Introduction at NIKHEF that originate from the ICES-KIS WTCW Virtual Laboratory project. The unprecedented increase in network bandwidth over the last decade has enabled novel ways of solving the NIKHEF contributes in the EDG project in half of the simulation and analysis problems for the LHC era. Tra- work packages (WP): Fabric Management (WP4), Test ditionally, the amount of computational power one bed Integration (WP6), Authorisation (WP6/WP7), could buy for the same price has doubled every 18 Networking (WP7), High-Energy Physics Applications months, a phenomenon known as Moore’s Law. But (WP8), and Project Management (WP12). the increase in wide-area network bandwidth has been Fabric Management much faster, doubling every 9-12 months. NIKHEF used the installation system provided by the The ‘Grid’ exploits this almost unlimited international EDG Fabric Management work package to install and bandwidth to interconnect compute clusters, large disk configure its Testbed1 computers. We were able to pro- caches, and tape robots scattered over a large geo- duce an excellent evaluation of the Local Configuration graphical area. This Grid can be used simultaneously by (LCFG) system after this exercise, since none of the many communities (also called Virtual Organisations), group knew anything about LCFG beforehand. like Alice, Atlas, D0 and LHCb. At the startup of LHC, the expected data rate after the level-3 trigger is ap- Another part ofFabricManagement is the ‘front end’ of proximately five petabytes per year for all the LHC ex- the compute cluster. All interaction between the Grid periments, and the total CERN-related analysis effort and the local centre will be through a single logical will require on the order of 50,000 high-end PCs in gateway. This allows for sophisticated scheduling tech- 2007. This effort will be distributed over all collabora- niques to be used inside a fabric to optimise computer tors, since no single institution will be able to support use. It will also protect the centre against cracking such a large-scale infrastructure. attempts and will support pluggable authorisation and dynamic account creation and mapping. NIKHEF personnel are involved in several Grid-related projects. Inside the fabric, monitoring and correlation tools will 5.2 DataGrid make a farm of thousands of nodes manageable and provide metrics on utilisation. For the current set of The European DataGrid (EDG) is a project funded by farms, load measurements have indicated large varia- the European Union with the aim of setting up a com- tions per experiment and per user; something that can putational and data-intensive grid of resources for the be balanced once the various farms are combined into analysis of data coming from scientific exploration. It one (see Fig. 5.1). started in January 2001 and is partially based on the successful Globus meta-computing toolkit, which provides basic ‘Grid’ services. The EDG project has been extending this basic set with the required functions for LHC computing: a resource broker, data replication and management, fabric management, grid-wide monitoring and networking. All these toolswill be available for the three data- intensive applications that drive DataGrid: the LHC experiments, whole-earth ozone profiling using earth- Figure 5.1: Farm load (# jobs running, blue line) and queue length (# jobs waiting, red line) for the 104-CPU observation satellite data (in collaboration with colleagues from the KNMI (The Netherlands)), and bio- NIKHEF D0 Farm. medical analysis. The first working test bed was de- ployed in November 2001, and NIKHEF was one of Testb ed Integration the first institutes with an operational system (along- side CERN, IN2P3, INFN and RAL). This ‘EDG Test The NIKHEF Testbed1 site currently comprises ten ma- bed1’will supplement the pre-existing Grid test beds chines. One of these is an installation server. Configu- ration instructions for the other machines are archived

83 network monitoring services. The other six have yet to be configured. Ten more high-end dual-processor machines are marked for inclusion in the Testbed once its configuration is complete. Security services When interconnecting a multitude of systems worldwide with high-speed connectivity, such a system will instantly become a valuable target for abuse. It is therefore important to do strong authentication of the users of such a system, and to make sure that authorisation reflects usage policies. The user authentication in the Grid is based on public- keycryptography and an associated Public Key Infra- structure (PKI) to distribute the keys. This system is well known from its role in e-commerce transactions, where sensitive financial data (credit card numbers) are encrypted such that only the intended recipient (the web trader) can read it. The Grid takes this technique one step further, and has also the individual end-users authenticate in this way. Using limited-lifetime ’prox- ies’, it has been successfully leveraged to provide ’single sign-on’ for all users on the Grid: you only need to type your pass phrase once at the beginning of the day, and all grid resources can be used without further hassle. NIKHEF provides trusted third-party services (the Cer- Figure 5.2: The NIKHEF DataGrid Testbed. Each tification Authority) for all Grid users in the Nether- of the boxes contains a complete dual-CPU machine lands, and is recognised as the authoritative Dutch with 40 GB hard disk and 896 MB RAM. The network Grid-CA in Europe. switches are located in the centre. Networking Aside from the network monitoring machine on the Testbed, Grid networking activities at NIKHEF are here, as are all the software packages which must be common across projects. They will be described in the installed. This machine broadcasts update or reconfig- DataTAG section below. uration notices to the other machines. Another machine runs a directory service (Lightweight Directory HEP Applications Access Protocol (LDAP)) that contains the mapping This work package (WP8) has been responsible for key of Grid users onto communities called Virtual Organ- projects in the past year. The first was the generation of isations (VOs). VOs are analogous to Unix ‘groups’; arequirements document. This document provides es- for example, a large storage area could be declared as sential direction for the project, as it defines the goal: writable by the LHCb VO. When this storage service re- What should the Grid be able to do for High-Energy ceives a write request from a grid user, it consults the Physics? The second project was making the first eval- NIKHEF VO server to verify that the user belongs to uation of Testbed1. NIKHEF appointed a full-time staff the LHCb VO, and accepts or denies the request based physicist to (WP8) in 2001, who participated fully in on the answer. The NIKHEF VO server is authoritative both these projects. for the entire EDG project. Since Testbed1 roll out was behind schedule, for two The other eight machines are high-end computers, each months all full-time WP8 personnel were temporar- with two GHz-class Pentium processors. Some of them ily reassigned to WP6 to provide deployment support. are visible in Fig. 5.2. One of them hosts the Grid NIKHEF’s decision to appoint a full-time WP8 person storage service (Storage Element), and another provides

84 has therefore been generously rewarded; the full-time middle ware layers such as information and security ser- WP8 people are among the best-informed in the project vices. The advance made will be disseminated into each because of this dual WP6/WP8 role. of the associated Grid projects. 5.3 AliEn AliEn is a grid prototype constructed by members of the Alice Collaboration at CERN. NIKHEF was the first site (outside of CERN) on which AliEn was successfully installed and this experience contributed valuable corrections to theAliEn design. NIKHEF allocated seven CPUs to the first AliEn production run in December, and they delivered about 43 CPU days of computing power. Grid techniques were used extensively, as the job execution commands were issued remotely from CERN and job output was stored on mass storage at CERN. 5.4 D0 Grid The 104-CPU D0 farm has been running efficiently for the past year; details of the Monte-Carlo production done with the farm can be found in the D0 section of this annual report. Besides D0, the farm has also been used to run Monte-Carlo production for Antares and L3. Trials with running the D0 Monte-Carlo production chain under the control of the Condor batch system were made this summer. Initial tests were successful, but it was not possible to run the production in full Grid fashion due to a limitation in the way the D0 software is constructed. Developers at Fermilab are currently trying to correct this situation and expect to have compatible software sometime in early 2002. 5.5 DataTAG The DataTag is a new project that will start in 2002. The fundamental objective of the DataTAG project is to create a large-scale intercontinental Grid test bed involving the DataGrid project, several national projects in Europe, and related Grid projects in the USA. This will allow to explore advanced networking technologies and interoperability issues between different Grid do- mains. The project will address the issues that arise in the sector of high performance inter-Grid networking, including sustained and reliable high performance data replication, end-to-end advanced network services, and novel monitoring techniques. The project will have its own dedicated Trans-Atlantic optical link of capacity 2.5Gbps between CERN and Starlight(Chicago). The project will also directly address the issues which arise in the sector of interoperability between the Grid

85 damping ring klystron linac module transportation system

beam transfer lines

RF wave- HV pulse guides cables

TESLA Tunnel Layout

86 6Future Projects: TESLA

6.1 Introduction offers the unique possibility to establish the coupling of the Higgs boson to itself. The precision of the mea- There is now worldwide consensus in the particle physics surements will be vital for the full understanding of the community that the next major accelerator after the origin of mass. LHC should be a linear e+e− collider. Further powerful tests of the Standard Model can be TESLA is one of the three projects under study. It is made by comparing the top quark mass, precisely mea- asuperconducting e+e− collider of 500 GeV total en- sured from a threshold scan, with much better measure- ergy, extendable to 800 GeV. The project includes an ments of the electroweak mixing angle sin2θ and of X-rayFreeElectron Laser facility. A schematic view of W the W boson mass, by lowering the energy of TESLA the layout is given in figure 6.1. The total length of the to 91 GeV (Giga-Z factory) and to around 161 GeV collider is approximately 33 km and it is proposed to (WW threshold scan), delivering 100 times more data be built adjacent to the DESY laboratory in Hamburg. at these energies than collected at LEP. The basic accelerating elements of TESLA are 9-cell superconducting Niobium cavities. More than 60 of Supersymmetry (SUSY) predicts many new particles, them have been routinely produced by industry, reach- partners of the matter and force particles that we know ing now an accelerating gradient well above the 23.4 today, and more than one Higgs boson. Although there MV/m needed for operation at the total collision energy is a large spectrum of masses for these supersymmetric of 500 GeV. A first 9-cell electro-polished cavity has particles, depending on the values of the parameters of reached a gradient of 35 MV/m, needed for 800 GeV the theory, again TESLA is complementary to the LHC operation. The design luminosity is 3.4 · 1034 cm−2s−1, in the sense that precision measurements of the masses almost 1000 times more than that reached at LEP2. and other properties of the particles accessible in the This is in part due to the extremely small sizes of the energy range of TESLA, will allow an accurate deter- electron and positron beams at the interaction point of mination of the parameters of the theory and therefore 553 nm and 5 nm in the horizontal and vertical plane its consistency and completeness over a large energy respectively. TESLA can also be operated as an e−e−, range. eγ or γγ collider with (effective) luminosities 15-20% − The physics case for TESLA and a possible detector of the e+e luminosity. have been worked out in a series of workshops and 6.2 Physics Motivation are reportedintheTESLATechnical Design Report. NIKHEF was involved in the study of the measurement The Higgs particle is expected to play a central role in of the branching ratio of the Higgs boson decaying into the experimental programme of TESLA. At 500 GeV two photons. This is an important decay mode to mea- collision energy a Standard Model (SM) Higgs boson sure, as it proceeds through (heavy) particle loops and of mass up to 400 GeV/c2 can be observed. This is is therefore very sensitive to new physics. It was shown well above the upper limit of about 200 GeV/c2 ob- that a relative uncertainty on this branching ratio of tained from precision measurements at LEP. If (SM) between 10% and 16% could be obtained for a Higgs Higgs(es) exist in this mass range they will be discov- mass of 120 GeV/c2.Together with a measurement of ered at the Large Hadron Collider under construction the total width of the Higgs boson, possible in the γγ at CERN (and possibly already at the Fermilab Teva- mode of operation of TESLA, a precision of 10% on tron collider). However, previous experience has shown the partial width of the Higgs boson decaying into γγ that proton-(anti)proton colliders and e+e− colliders is feasible. are complementary. The W and Z bosons were discovered at the SppS¯ collider of CERN in the early eighties. 6.3 Detector R&D But precision measurements at LEP of the properties The ECFA-DESY workshop is continuing with special of the Z and W bosons really established the Standard emphasis on higher energies up to 1 TeV, on γγ, eγ Model, allowing a precise prediction of the top quark and e−e− options, and on the detector design following mass and to constrain the Higgs boson mass. Even if further detector R&D. Important aspects of the detec- the Higgs is discovered before at the LHC, the clean − tor design are related to track momentum resolution, experimental conditions of the e+e collider allow pre- vertexing, energy flow and hermiticity. The proposed cise determination of its properties like mass, width, TESLA detector therefore consists of a very high pre- spin, decay branching fractions. In addition, TESLA

87 cision vertex detector, surrounded and complemented in the forward directions by several additional layers of Silicon detectors, a large tracking volume covered by aTimeProjection Chamber (TPC), and a high granu- larity calorimeter, all embedded in a 4 Tesla solenoidal magnetic ﬁeld. e+ NIKHEF just started with investigating the feasibility of a highly segmented readout of the TPC by means of pixel detectors. The studies by NIKHEF of a beam damping ring protection system are discussed in the next section. 6.4 Investigation into a beam protection system for TESLA Special about the high-energy high luminosity beam are the intense (4 nC) electron bunch and a small (less linear accelerator than 100 µm) beam diameter. The long response time (more than 50 µs) precludes swift action in case of miss-steering. An oﬀ-axis electron beam, hitting a surface, will cause irreversible mechanical damage by im- positron pulse heating. The radiation induced heat load for the preaccelerator cryogenic beam-line components due to a beam ‘halo’ should be many orders of magnitude lower than for a electron-positron collision room temperature accelerating structure. NIKHEF pro- high energy physics experiments posed to apply its MEA Protective Collimator Compton 33 km Battery system (PCCB system) for TESLA. This sen- positron source x-ray laser sitive system consisted of maintenance free radiation e- hard components. The success of its performance has aux. positron and been demonstrated by the complete absence of radi- 2nd electron source ation activation of beam-line components after more than 15 years of MEA operation. The proposed PCCB system consists of many protection collimators located at strategic places along the beam line. A ‘scraping’ electron beam generates a photon shower. The shower is converted in a thin aluminium sheet into Compton- electrons. The Compton-electrons are collected by a lead absorber and converted into an external electrical current. A full beam pulse may produce more than damping ring

100 V pulses into a 50-ohm load. The minimum pulse linear accelerator output is limited by external electrical noise, typically 1 mV. The sensitivity for a sustained miss-steered beam e- is several orders better. Our design was tested at the Tesla Test Facility and the results are promising. The electron sources results were presented to the TESLA collaboration. (HEP and x-ray laser)

H.Weise 3/2000

Figure 6.1: Sketch of the overall layout of TESLA (the second interaction region with crossing angle is optional and not part of the baseline design).

88 EPublications, Theses and Talks 1Publications

[1] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; Search for large extra dimensions in dielectron and dipho- Ahmed, S.N.; Duensing, S.; Filhaut, F.; Wijngaarden, ton production D.A.; D0 collaboration Phys. Rev.Lett. 86 (2001) 1156-1161 Differential cross section for W boson production√ as a [11] Abbott B. (et al.);Balm,P.W.;Peters,O.; Duensing, S.; function of transverse momentum in ppc¯ ollisions at s =1.8 Wijngaarden, D.A.; D0 collaboration TeV Inclusive jet production in pp collisions Phys. Lett. B 513 (2001) 292-300 Phys. Rev.Lett. 86 (2001) 1707-1712 [2] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; [12] Abbott B. (et al.);Balm,P.W.;Peters,O.; Duensing, S.; Ahmed, S.N.; Jong, S.J. de; Duensing, S.; Filhaut, F.; Wijngaarden, D.A.; D0 collaboration Wijngaarden, D.A.; D0 collaboration Measurement of the angular distribution of electrons√ from Search for heavy particles decaying into electron-positron W → eν decays observed in ppc¯ ollisions at s =1.8 TeV pairs in ppc¯ ollisions Phys. Rev. D63(2001) 072001 Phys. Rev.Lett. 87 (2001) 061802 [13] Abbott, B. (et al.);Balm,P.W.;Bos,K.;Peters, O.; [3] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; Duensing, S.; Filhaut, F.; Wijngaarden, D.A.; D0 collab- Ahmed, S.N.; Jong, S.J. de; Duensing, S.; Filhaut, F.; oration Wijngaarden, D.A.; D0 collaboration √ AQuasi-Model-Independent Search for New High pT Physics High-pT Jets in ppCollisions at s =630 and 1800 GeV at D0 Phys. Rev. D64(2001) 032003 Phys. Rev.Lett. 86 (2001) 3712-3717 [4] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; [14] Abbott, B. (et al.);Duensing, S.; Wijngaarden, D.A.; D0 Ahmed, S.N.; Jong, S.J. de; Duensing, S.; Filhaut, F.; Collaboration √ Wijngaarden, D.A.; D0 collaboration Ratios of multijet cross-sections in ppc¯ ollisions at s =1.8 Measurement of the ratio of differential cross sections for TeV WandZbosonproduction as√ a function of transverse Phys. Rev.Lett. 86 (2001) 1955 momentum in ppcollisions at s =1.8 TeV [15] Abbott, B. (et al.);Duensing, S.; Wijngaarden, D.A.; D0 Phys. Lett. B 517 (2001) 299-308 Collaboration √ [5] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; The ratio of jet cross-sections at s =630 GeV and 1800 Ahmed, S.N.; Jong, S.J. de; Duensing, S.; Filhaut, F.; GeV Wijngaarden, D.A.; D0 collaboration Phys. Rev.Lett. 86 (2001) 2523 Search for single top quark production at D0 using neural [16] Abbot, B; (et al.);Balm,P.W.;Bos,K.;Peters, O.; networks Duensing, S.; Filhaut, F.; Wijngaarden, D.A.; D0 col- Phys. Lett. B 517 (2001) 282-294 laboration [6] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; Quasi-model-independent search for new physics at large Ahmed, S.N.; Jong, S.J. de; Duensing, S.; Filhaut, F.; transverse momentum Wijngaarden, D.A.; D0 collaboration Phys. Rev. D64(2001) 012004 Search for first-generation scalar and vector leptoquarks [17] Abdallah, J. (et al.);Blom,H.M.;Ferreira-Montenegro, Phys. Rev. D64(2001) 092004 J.; Kluit, P.; Mulders, M.; Reid, D.; Timmermans, J.; [7] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; Dam, P. van; Eldik, J. van; Vulpen, I. van; DELPHI Col- Ahmed, S.N.; Jong, S.J. de; Duensing, S.; Filhaut, F.; laboration Wijngaarden, D.A.; D0 collaboration Search for technicolor with DELPHI Search for new physics using QUAERO: a general interface Eur. Phys. J. C22(2001) 17-29 to D0 event data [18] Abele, A. (et al.);Hessey, N.; The CrystalBarrel Collab- Phys. Rev.Lett. 87 (2001) 231801 oration [8] Abazov, V.M. (et al.);Balm,P.W.;Bos,K.;Peters,O.; Measurement oftheradiative decay omega to eta gamma Ahmed, S.N.; Jong, S.J. de; Duensing, S.; Filhaut, F.; in proton-antiproton annihilation at rest Wijngaarden, D.A.; D0 collaboration Phys. Rev. D61(2000) 032002 √Ratio of isolated photon cross sections in ppc¯ ollisions at [19] Abele, A (et al.):Hessey, N.; The CrystalBarrelCollabo- s =630 and 1800 GeV ration Phys. Rev.Lett. 87 (2001) 251805 Test of NN potential models: Isospinrelationsin antipro- [9] Abbott B. (et al.);Balm,P.W.;Peters,O.; Duensing, S.; ton deuterium annihilations at rest and the search for Wijngaarden, D.A.; D0 collaboration quasinuclear bound states Search for electroweak production of single top quarks in Eur. Phys. J. C17(2000) 583 pp collisions [20] Abele, A. (et al.);Hessey, N.; The CrystalBarrel Collab- Phys. Rev. D63(2001) 031101 oration [10] Abbott B. (et al.);Balm,P.W.;Peters, O.; Duensing, S.; Study of f0 Decays into Four Neutral Pions Wijngaarden, D.A.; D0 collaboration Eur. Phys. J. C19(2001) 667

89 √ [21] Abele, A. (et al.);Hessey, N.; The CrystalBarrel Collab- s =189 GeV oration Phys. Lett. B 500 (2001) 22-36 High resolution search for the tensor glueball candidate [32] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; ξ(2230) Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Phys. Lett. B 520 (2001) 175 Eldik, J. van; Vulpen, I. van; DELPHI Collaboration [22] Abele, A. (et al.);Hessey, N.; The CrystalBarrel Collab- Update of the search for supersymmetric particles in sce- oration narios with gravitino LSP and sleptons NLSP Branching ratios for ppa¯ nnihilation at rest into two-body Phys. Lett. B 503 (2001) 34-48 final states [33] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Nucl. Phys. A 679 (2001) 563 Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; [23] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Study of dimuon production in photon-photon collisions Eldik, J. van; Vulpen, I. van; DELPHI Collaboration and measurement of QED photon structure functions at Search for a fermiophobic Higgs at LEP2 LEP Phys. Lett. B 507 (2001) 89-103 Eur. Phys. J. C19(2001) 15-28 [24] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; [34] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Eldik, J. van; Vulpen, I. van; DELPHI Collaboration + − Measurement of the semileptonic b branching fractions Measurement oftheZZcross-section in e e interactions and average b mixing parameter in Z decays at 183-189 GeV Eur. Phys. J. C20(2001) 455-478 Phys. Lett. B 497 (2001) 199-213 [25] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; [35] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Eldik, J. van; Vulpen, I. van; DELPHI Collaboration√ + − ¯0 ∗+ − Search for sleptons in e e collisions at s =183 to 189 Measurement of Vcb from the decay process B → D ν¯ Phys. Lett. B 510 (2001) 55-74 GeV Eur. Phys. J. C19(2001) 29-42 [26] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; [36] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Measurement of the√ Mass and Width of the W Boson in √ e+e- Collisions at s =189 GeV Search for neutralino pair production at s =189 GeV Phys. Lett. B 511 (2001) 159-177 Eur. Phys. J. C19 (2001) 201 [27] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; [37] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Eldik, J. van; Vulpen, I. van; DELPHI Collaboration√ Ameasurementofthetautopological branching ratios Search for Spontaneous R-parity violation at s =183 Eur. Phys. J. C20(2001) 617-637 GeV and 189 GeV Phys. Lett. B 502 (2001) 24 [28] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; [38] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, Eldik, J. van; Vulpen, I. van; DELPHI Collaboration F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, Measurement of Trilinear Gauge Boson Couplings WWV , (V ≡ A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, Z,γ) in e+e− Collisions at 189 GeV A.C.; Mangeol,D.;Metzger,W.J.;Petersen,B.;Roux, Phys. Lett. B 502 (2001) 9-23 B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; [29] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Wilkens, H.; Buijs, A.; L3 collaboration Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Measurement ofthetaubranching fractions into leptons Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Phys. Lett. B 507 (2001) 47-60 Single Intermediate Vector Boson Production in e+e− √ [39] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- collisions at s =183 and 189 GeV ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, Phys. Lett. B 515 (2001) 238-254 F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, [30] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; Mangeol, D.; Metzger, W.J.; Petersen, B.; Sanders, M.P.; Eldik, J. van; Vulpen, I. van; DELPHI Collaboration Schotanus, D.J.; Timmermans, C.; Wilkens, H.; Buijs, A.; Search for the Standard Model Higgs boson at LEP in the L3 collaboration + − year 2000 Study√ of Z Boson Pair Production in e e Interactions Phys. Lett. B 499 (2001) 23-37 at s =192-202 GeV [31] Abreu, P. (et al.);Blom,H.M.;Boudinov, E.; Kluit, P.; Phys. Lett. B 497 (2001) 23-38 Mulders, M.; Reid, D.; Timmermans, J.; Dam, P. van; [40] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- Eldik, J. van; Vulpen, I. van; DELPHI Collaboration ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, Search for R-parity violation with a UDDcoupling at F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs,

90 A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; Mangeol,D.;Metzger,W.J.;Petersen,B.;Roux, A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Roux, B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; Van de Walle, R.T.; Wilkens, H.; Buijs, A.; L3 collabora- Wilkens, H.; Buijs, A.; L3 collaboration tion Measurement of the charm production cross section in γγ Measurement of the topological branching fractions of the collisions at LEP τ lepton at LEP Phys. Lett. B 514 (2001) 19-28 Phys. Lett. B 519 (2001) 189-198 [41] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- [47] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Sanders, M.P.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; Wilkens, H.; Buijs, A.; Schotanus, D.J.; Timmermans, C.; Wilkens, H.; Buijs, A.; L3 collaboration L3 collaboration + − Search for heavy isosinglet neutrino in e e annihilation Measurements of the cross sections for√ open charm and at LEP beauty production in γγ collisions at s =189-202 GeV Phys. Lett. B 517 (2001) 67-74 Phys. Lett. B 503 (2001) 10-20 [42] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- [48] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, F.C.; Filthaut, F.; Gulik, R. van; Jong, P. de; Linde, F.L.; F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, Muijs, A.J.M.; Dalen, J.A. van; Hu, Y.; Kittel, W.; König, A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Roux, A.C.; Mangeol,D.;Metzger,W.J.;Petersen,B.;Roux, B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; Van de Walle, R.T.; Wilkens, H.; Buijs, A.; L3 collabora- Wilkens, H.; Buijs, A.; L3 collaboration tion Search for neutral Higgs bosons of the minimal supersym-√ Search for heavy neutral and charged leptons in e+e− an- metric standard model in e+e− Interactions at s =192- nihilation at LEP 202 GeV Phys. Lett. B 517 (2001) 75-85 Phys. Lett. B 503 (2001) 21-33 [43] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- [49] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, F.C.; Filthaut, F.; Gulik, R. van; Jong, P. de; Linde, F.L.; F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, Muijs, A.J.M.; Dalen, J.A. van; Hu, Y.; Kittel, W.; König, A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Roux, A.C.; Mangeol,D.;Metzger,W.J.;Petersen,B.;Roux, B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; Van de Walle, R.T.; Wilkens, H.; Buijs, A.; L3 collabora- Wilkens, H.; Buijs, A.; L3 collaboration 0 ± ∓ + − tion Light resonances in Ks K π and ηπ π final states in Standard model Higgs boson with the L3 experiment at γγ collisions at LEP LEP Phys. Lett. B 501 (2001) 1-11 Phys. Lett. B 517 (2001) 319-331 [50] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- [44] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; Mangeol,D.;Metzger,W.J.;Petersen,B.;Roux, A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Roux, B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; Wilkens, H.; Buijs, A.; L3 collaboration 0 0 Wilkens, H.; Buijs, A.; L3 collaboration Ks Ks Finalstate in two photon collisions and implications Study of the e+e− → Zγγ → qqγγ Process at LEP for glueballs Phys. Lett. B 505 (2001) 47-58 Phys. Lett. B 501 (2001) 173-182 [45] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- [51] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Roux, A.C.; Mangeol,D.;Metzger,W.J.;Petersen,B.;Roux, B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; Wilkens, H.; Buijs, A.; L3 collaboration Wilkens, H.; Buijs, A.; L3 collaboration √ Total cross section in γγ collisions at LEP Search for excited leptons in e+e− interactions at s =192- Phys. Lett. B 519 (2001) 33-45 202 GeV [46] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- Phys. Lett. B 502 (2001) 37-50 ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, [52] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- F.C.; Filthaut, F.; Gulik, R. van; Jong, P. de; Linde, F.L.; ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, Muijs, A.J.M.; Dalen, J.A. van; Hu, Y.; Kittel, W.; König, F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs,

91 A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, HERMES collaboration A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Roux, Single spin azimuthal asymmetries in electroproduction of B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; neutral pions in semiinclusive deep inelastic scattering Wilkens, H.; Buijs, A.; L3 collaboration Phys. Rev. D64(2001) 097101 Search for the standard model Higgs boson in e+e− col- √ [61] Airapetian, A. (et al.); Amarian, M.; Aschenauer,E.C.; lisions at supto202GeV Bulten, H.J.; Witt Huberts, P.K.A. de; Ferro-Luzzi, M.; Phys. Lett. B 508 (2001) 225-236 Garutti, E.; Heesbeen, D.; Hesselink, W.H.A.; Hoffmann- [53] Acciarri, M. (et al.);Baldew,S.V.;Bobbink, G.J.; Dier- Rothe, P.; Ihssen, H.; Kolster, H.; Laziev, A.; Simani, C.; ckxsens, M.; Dierendonck, D.N. van; Duinker, P.; Erne, Steijger, J.J.M.; Brand, J.F.J. van den; Steenhoven, G. F.C.; Gulik, R. van; Jong, P. de; Linde, F.L.; Muijs, van der; Hunen, J.J. van; Visser, J.; HERMES collabora- A.J.M.; Dalen, J.A. van;Hu,Y.;Kittel,W.;König, tion A.C.; Mangeol, D.; Metzger, W.J.; Petersen, B.; Roux, Multiplicity of charged and neutral pions in deep-inelastic B.; Sanders, M.P.; Schotanus, D.J.; Timmermans, C.; scattering of 27.5 GeV positrons on hydrogen Wilkens, H.; Buijs, A.; L3 collaboration Eur. Phys. J. C21(2001) 599-606 Search for R-parity violating√ decays of supersymmetric + − [62] Airapetian, A. (et al.); Amarian, M.; Aschenauer,E.C.; particles in e e collisions at s =189 GeV Bulten, H.J.; Witt Huberts, P.K.A. de; Ferro-Luzzi, M.; Eur. Phys. J. C19(2001) 397-414 Garutti, E.; Heesbeen, D.; Hesselink, W.H.A.; Kolster, H.; [54] Adam, W. (et al.);Eijk,B.van;Hartjes,F. Laziev, A.; Simani, C.; Steijger, J.J.M.; Brand, J.F.J. van Diamond pixel detectors den; Steenhoven, G. van der; Hunen, J.J. van; Visser, J.; Nucl. Instr. Meth. A 465 (2001) 88-91 HERMES collaboration [55] Afanasev, S.V. (et al.);Leeuwen, M. van; NA49 collabo- Measurement of the beam-spin azimuthal asymmetry as- ration sociated with deeply-virtual Compton scattering Event-by-event fluctuations of the kaon to pion ratio in Phys. Rev.Lett. 87 (2001) 182001 central Pb+Pb collisions at 158-GeV per nucleon. [63] Airapetian, A. (et al.); Amarian, M.; Aschenauer,E.C.; Phys. Rev.Lett. 86 (2001) 1965-1969. Bulten, H.J.; Witt Huberts, P.K.A. de; Ferro-Luzzi, M.; [56] Aggarwal, M.M. (et al.);Buijs, A.; Eijndhoven, N.J.A.M. Garutti, E.; Heesbeen, D.; Hesselink, W.H.A.; Kolster, H.; van; Geurts, F.J.M.; Kamermans, R.; Pijll, E. van der; Laziev, A.; Simani, C.; Steijger, J.J.M.; Brand, J.F.J. van WA98 Collaboration den; Steenhoven, G. van der; Hunen, J.J. van; Visser, J.; Localized charged-neutral fluctuations in 158 A GeV Pb HERMES collaboration Measurement of longitudinal spin transfer to Lambda hy- plus Pb collisions Phys. Rev. C64(2001) 011901 perons in deep-inelastic lepton scattering Phys. Rev. D64(2001) 112005 [57] Aggarwal, M.M. (et al.);Eijndhoven, N.J.A.M. van; Kamer- mans, R.; Pijll, E.C. van der; WA98 collaboration [64] Akhmedov, E.K.; Silva-Marcos, J.I. Scaling of Particle and Transverse Energy Production in Neutrino masses and mixing with seesaw mechanism and universal breaking of extended democracy Pb+Pb Collisions at 158 A GeV Eur. Phys. J. C18(2001) 651 Phys. Lett. B 498 (2001) 237-250 [58] Airapetian, A. (et al.); Amarian, M.; Aschenauer,E.C.; [65] Arkhipov V.A. (et al.) ;Boer-Rookhuizen, H.; Heine, Bulten, H.J.; Witt Huberts, P.K.A. de; Ferro-Luzzi, M.; E.; Heubers, W.P.J.; Kaan, A.P.; Kroes, F.B.; Kuijer, Garutti, E.; Heesbeen, D.; Hesselink, W.H.A.; Hoffman- L.H.; Laan, J.B. van der; Langelaar, J.; Louwrier, P.W.F.; Rothe, P.; Ihssen, H.; Kolstein, M.; Kolster, H.; Laziev, Luijckx, G.; Maas, R.; Middelkoop, G. van; Noomen, J.G.; A.; Simani, C.; Steijger, J.J.M.; Brand, J.F.J. van den; Spelt, J.B. Steenhoven, G. van der; Hunen, J.J. van; Visser, J.; HER- Project of the Dubna Electron Synchrotron MES collaboration Nucl. Instr. Meth. A 467-468 (2001) 59-62 Part 1 Hadron formation in deep-inelastic positron scattering in [66] Arkhipov V.A. (et al.) ;Boer-Rookhuizen, H.; Heine, a nuclear environment E.; Heubers, W.P.J.; Kaan, A.P.; Kroes, F.B.; Kuijer, Eur. Phys. J. C20(2001) 479-486 L.H.; Laan, J.B. van der; Langelaar, J.; Louwrier, P.W.F.; [59] Airapetian, A. (et al.); Amarian, M.; Aschenauer,E.C.; Luijckx, G.; Maas, R.; Middelkoop, G. van; Noomen, J.G.; Bulten, H.J.; Witt Huberts, P.K.A. de; Ferro-Luzzi, M.; Spelt, J.B. Garutti, E.; Heesbeen, D.; Hesselink, W.H.A.; Kolster, H.; Project of the Dubna electron synchrotron Nucl. Instr. Meth. A 470 (2001) 1-6 Laziev, A.; Simani, C.; Steijger, J.J.M.; Brand, J.F.J. van den; Steenhoven, G. van der; Hunen, J.J. van; Visser, J.; [67] Aniol, K.A. (et al.);Templon,J. HERMES collaboration New measurement of parity violation in elastic electron- Double-spin asymmetry in the cross section for exclusive proton scattering and implications for strange form factors ρ0 production in lepton-proton scattering Phys. Lett. B 509 (2001) 211-216 Phys. Lett. B 513 (2001) 301-310 [68] Antinori, F. (et al.);Kamermans, R.; Kuijer, P.G.; Schillings, [60] Airapetian, A. (et al.); Amarian, M.; Aschenauer,E.C.; E.; Ven, P.vande;NA57collaboration Bulten, H.J.; Witt Huberts, P.K.A. de; Ferro-Luzzi, M.; Study of the production of Strange and Multi-Strange Par- Garutti, E.; Heesbeen, D.; Hesselink, W.H.A.; Kolster, H.; ticles in Lead-Lead Interactions at the CERN SPS: the Laziev, A.; Simani, C.; Steijger, J.J.M.; Brand, J.F.J. van NA57 Experiment. den; Steenhoven, G. van der; Hunen, J.J. van; Visser, J.; Nucl. Phys. A 681 (2001) 165-173

92 [69] Antinori, F. (et al.);Kamermans, R.; Kuijer, P.G.; Schillings, [79] Boos, E. (et al.);Reid,D.W. E.; NA57 collaboration Measuring the Higgs branching fraction into two photons Determination of the event centrality in the WA97 and at future linear e+e− colliders NA57 experiments Eur. Phys. J. C19(2001) 455-461 J. Phys. G27(2001) 391-396 [80] Botje, M. [70] Antinori, F. (et al.);Kamermans, R.; Kuijer, P.G.; Schillings, Error propagation in QCD fits E.; Ven, P.vande;NA57collaboration Proc. DIS 2000, Ed. by J.A. Gracey, T. Greenshaw. 165- Status of the NA57 experiment at CERN SPS 167 J. Phys. G27(2001) 383-390 [81] Branford, D. (et al.);Ireland, D.G.; Jager,C.W.de;Kas- [71] Apeldoorn, G. van (et al.);Bakel,N.van;Bauer,T.S.; dorp, W.J.; Lác, J; Lapikás; Steenhoven, G. van der Beuzekom, M. van; Boer Rookhuizen, H.; Brand, J.F.J. Electron- and photon-induced proton knockout from 209Bi van den; Bulten, H.J.; Doets, M.; Eijk, R. van den ; Gouz, Phys. Rev. C63(2001) 014310 I.; Groen, P. de; Gromov, V.; Hierck, R.; Hommels, L.; [82] Breitweg, J. (et al.);Bokel,C.;Botje, M.; Bruemmer, Jans, E.; Jansen, L.; Kaan, A.P.; Ketel, T.J.; Klous, S.; N.; Engelen, J.; Grijpink, S.; Koffeman, E.; Kooijman, Koene, B.; Kraan, M.; Kroes, F.; Kuijt,J.;Merk,M.;Mul, P.; Schagen, S.; Sighem, A. van; Tiecke, H.; Tuning, W.; F.; Needham, M.; Schuijlenburg, H.; Sluijk, T.; Tilburg, Velthuis, J.J.; Vossebeld, J.; Wiggers,L.;Wolf,E.de; J. van; Verkooyen, J.; Vries, H.de;Wiggers,L.;Saitsev, ZEUS Collaboration N.; Zupan M. Measurement of dijet production in neutral current deep LHCb VELO Technical Design Report, CERN/LHCC 2001- 2 inelastic scattering at high Q and determination of αs 011 Phys. Lett. B 507 (2001) 70-88 ISBN 92-9083-179-X, 31 May 2001. [83] Breitweg, J. (et al.);Bokel,C.;Botje, M.; Bruemmer, [72] Apeldoorn, G. van (et al.);Arink,R.;Bakel, N. van; N.; Engelen, J.; Grijpink, S.; Koffeman, E.; Kooijman, P.; Bauer, T.S.; Berkien, A.; Born, E. van den; Brand, J.F.J. Schagen, S.; Sighem, A. van; Tassi. E.; Tiecke, H.; Tun- van den; Bulten, H.J.; Carlogano, C.; Ceelie, L.; Doets, ing, W.; Velthuis, J.J.; Vossebeld, J.; Wiggers, L.; Wolf, M.; Eijk, R. van den ; Gouz, I.; Groen, P. de; Gromov, E. de; ZEUS Collaboration V.; Hierck, R.; Hommels, L.; Jans, E.; Ketel, T.J.; Klous, Measurement of openbeautyproduction in photoproduc- S.; Koene, B.; Kruiper, H.; Merk, M.; Mul, F.; Needham, tion at HERA M.;Petten, O. van; Schuijlenburg, H.; Sluijk, T.; Stolte, Eur. Phys. J. C18(2001) 625-637 J.; Tilburg, J. van; Vries, H. de; Wiggers, L.; Wijk, R. van; Zupan M.; Zwart, A. [84] Breitweg, J. (et al.);Bokel,C.;Botje, M.; Bruemmer, LHCb Outer Tracker Technical Design Report, CERN/LHCC N.; Engelen, J.; Grijpink, S.; Koffeman, E.; Kooijman, P.; 2001-024 Schagen, S.; Sighem, A. van; Tassi. E.; Tiecke, H.; Tun- ISBN 92-9083-200-2, 14 September 2001. ing, W.; Velthuis, J.J.; Vossebeld, J.; Wiggers, L.; Wolf, E. de; ZEUS Collaboration [73] Atayan, M.R. (et al.);Kittel,W.;EHS-NA22 collaboration Measurement of dijet cross sections for events with a lead- Transverse energy flow in meson-proton and meson-nucleus ing neutron in photoproduction at HERA interactions at 250 GeV/c Nucl. Phys. B 596 (2001) 3-29 Eur. Phys. J. C21(2001) 271-279 [85] Brown, H.N. (et al.);Timmermans, C.; E821 Collabora- [74] Ballaminut A.(et al.);Koeper,D. tion WIRED - World Wide Web interactive remote event dis- Precise measurement of the positive muon anomalous play magnetic moment Comput. Phys. Commun. 140 (2001) 266-273 Phys. Rev.Lett. 86 (2001) 2227 [75] Bardelloni, G. (et al.);Boerkamp,A.L.J.;Calvet,D.;Viss- [86] Buontempo, S. (et al.);Uiterwijk,J.W.E. chers, J.L. The compact emulsion spectrometer Anewread-outsystem for an imaging pixel detector Nucl. Instr. Meth. A 457 (2001) 464-470 Proc. IEEE Nuclear Science Symposium and Medical [87] Burckhart, H.; Hart, R.; Jones, V.; Khomoutnikov, V.; Imaging Conf., Lyon, France, 15-20 Oct. 2000. h12.57-60 Ryabov, Y. [76] Barton, R.A.; (et al.);vanLeeuwen,M.;Botje,M.;NA49 Communication between Trigger/DAQ and DCS in AT- Collaboration LAS Production of multi-strange hyperonsandstrange reso- Proc. Int. Conf. on Computing in HighEnergyand Nu- nances in the NA49 experiment. clear Physics, Ed. H.S. Chen, Beijing, China, 3-7 Sept. J. Phys. G27(2001) 367-374 2001, p. 109 [77] Beuzekom, M.G. van; Garutti, E.; Heesbeen, D.; Steijger, [88] Buuren, L.D. van; 97-01 collaboration J.J.M.; Visser, J. Measurement ofspinparameters in the ∆ region for the −→ −→ First experience with the HERMES silicon detector 1 H ( e , e ) reaction. Nucl. Instr. Meth. A 461 (2001) 247-250 Proc. 16th Int. Conf. on Few-BodyProblemsinPhysics (FB 16), Taipei, Taiwan, China, 6-10 Mar. 2000 [78] Boer, F.W.N. de (et al.);Dantzig,R.van Nucl. Phys. A 684 (2001) 324c-326c Further search for a neutral bosonwithamassaround 9 MeV/c2 [89] Buuren, L.D. van; Szczerba, D.; van den Brand, J.F.J.; J. Phys. G27(2001) L29-L40 Bulten, H.J.; Ferro-Luzzi, M.; Klous, S.; Kolster, H.;

93 Lang, J.; Mul, F.A.; Poolman, H.R.; Simani, M.C. Proc. Europhysics Neutrino Oscillation Workshop (NOW Performance ofahydrogen/deuterium polarizedgastar- 2000), Conca Specchiulla, Otranto, Lecce, Italy, 9-16 Sep get in a storage ring 2000, Nucl. Instr. Meth. A 474 (2001) 209-223 Nucl. Phys. B(Proc.Suppl.) 100 (2001) 341-343 [90] Carloganu, C. [99] Dinapoli, R. (et al.);San Segundo Bello, D. Study of atmospheric neutrino oscillations in ANTARES Afront-end for silicon pixel detectors in ALICE and LHCb Nucl. Phys. B(Proc.Suppl.) 100 (2001) 145-147 Nucl. Instr. Meth. A 461 (2001) 492-495 [91] Chekanov, M. (et al.);Bokel,C.;Botje,M.;Engelen, [100] Doerrzapf, M.; Gato-Rivera, B. J.; Grijpink, S.; Koffeman, E.; Kooijman, P.; Schagen, Singular dimensions of the N=2 superconformal algebras S.; Sighem, A. van; Tassi, E.; Tiecke, H.; Tuning, W.; II: The twisted N=2 algebra Velthuis, J.J.; Vossebeld, J.; Wiggers, L.; Wolf, E. de; Commun. Math. Phys. 220 (2001) 263-292 ZEUS Collaboration [101] Eskut, E. (et al.);Dantzig,R.van; Konijn, J.; Melzer, Multiplicity moments in deep inelastic scattering at HERA O.; Oldeman, R.G.D.; Pesen, E.; Poel, C.A.F.J. van der; Phys. Lett. B 510 (2001) 36-54 Uiterwijk, J.W.E.; Visschers,J.L.; CHORUS collaboration [92] Chekanov, M. (et al.);Bokel,C.;Botje,M.;Engelen, New results from a search for νµ → ντ and νe → ντ J.; Grijpink, S.; Koffeman, E.; Kooijman, P.; Schagen, oscillation S.; Sighem, A. van; Tassi, E.; Tiecke, H.; Tuning, W.; Phys. Lett. B 497 (2001) 8-22 Velthuis, J.J.; Vossebeld, J.; Wiggers, L.; Wolf, E. de; [102] Eskut, E. (et al.);Dantzig,R.van;Jong,M.de;Konijn, ZEUS Collaboration J.; Melzer, O.; Oldeman, R.G.D.; Pesen, E.; Poel, C.A.F.J. Study of the effective transverse momentum of partons in van der; Uiterwijk, J.W.E.; Visschers, J.L.; CHORUS col- the proton using prompt photons in photoproduction at laboration HERA Observation of weak neutral current neutrino production Phys. Lett. B 511 (2001) 19-32 of J/ψ [93] Chekanov, M. (et al.);Bokel,C.;Engelen,J.;Grijpink, Phys. Lett. B 503 (2001) 1-9 S.; Maddox, E.; Koffeman, E.; Kooijman, P.; Schagen, S.; [103] Filthaut, F. Tassi, E.; Tiecke, H.; Tuning, W.; Velthuis, J.J.; Wiggers, Production and testing of the D0 silicon microstrip tracker L.; Wolf, E. de; ZEUS Collaboration Proc. IEEE Nuclear Science Symposium And Medical Three-jet production in diffractive deep inelastic scattering ImagingConf., Lyon, France, 15-20 oktober 2000, Ed. at HERA J.D. Valentine, Piscataway, IEEE, 2001, Phys. Lett. B 516 (2001) 273-292 IEEE Trans. Nucl. Sci. 48 (2001) 1002 [94] Chekanov, M. (et al.);Bokel,C.;Botje,M.; Bruemmers, [104] Fissum, K.G. (et al.);Templon,J.A. N.; Engelen, J.; Grijpink, S.; Koffeman, E.; Kooijman, P.; Vertical drift chambers for the Hall A high-resolution spec- Schagen, S.; Sighem, A. van; Tassi, E.; Tiecke, H.; Tun- trometers at Jefferson Lab ing, W.; Velthuis, J.J.; Vossebeld, J.; Wiggers, L.; Wolf, Nucl. Instr. Meth. A 474 (2001) 108-131 E. de; ZEUS Collaboration Search for resonance decays to a ν¯ plus jet in e+pscat- [105] Fornaini, A.; Calvet, D.; Visschers, J.L. tering at DESY HERA Soft X-ray sensitivity of a photon-counting hybrid pixel Phys. Rev. D63(2001) 052002 detector with asilicon sensor matrix Nucl. Instr. Meth. A 466 (2001) 142-145 [95] Chekanov, S. (et al.);Bokel,C.;Engelen, J.; Grijpink, S.; Maddox, E.; Koffeman, E.; Kooijman, P.; Schagen, S.; [106] Gaskell, D. (et al.);VolmerJ.,Zihlman B. 1 Tassi, E.; Tiecke, H.; Tuning, W.; Velthuis, J.J.; Wiggers, Longitudinal Electroproduction of Charged Pions from H, 2 3 L.; Wolf, E. de; ZEUS Collaboration H, and He Phys. Rev.Lett. 87 (2001) 202301 Measurement of the neutral current cross section and F2 structure function for deep inelastic e+pscattering at [107] Gaskell, D. (et al.);VolmerJ. HERA Measurement of longitudinal and transverse cross sections Eur. Phys. J. C21(2001) 443-471 in the 3He(e,e’π+)3Hreaction at W = 1.6 GeV [96] Dalen, J.A. van Phys. Rev. C65(2001) 011001R Bose-Einstein correlations in W-pair production at LEP: [108] Greene, B.R.; Schalm, K.; Shiu, G. results from L3 and OPAL Dynamical topologychange in M theory Proc. IX Int.WorkshoponMultiparticle Production J. Math. Phys. 42 (2001) 3171-3187 “New frontiers in soft physics and correlations on the [109] Groep, D.L.(et al.);Batenburg, M.F. van; Bauer, Th.S.; threshold of the third millennium”, Villa Gualino, Torino, Blok, H.; Boersma, D.J.; Heimberg, P.; Hesselink, W.H.A.; Italy, Jans, E.; Lapikás, L.; Onderwater, C.J.G.; Starink, R.; Nucl. Phys. B(Proc.Suppl.) 92 (2001) 247 Steenbakkers, M.F.M.; Vries, H. de [97] Danby, G.T. (et al.);Timmermans,C.;E821Collabora- Investigation of the Exclusive 3He(e, epp) Reaction tion Phys. Rev. C63(2001) 014005 The Brookhaven muon storage ring magnet [110] Groot Nibbelink, S.; Nyawelo, T.S.; Holten, J.W. van Nucl. Instrum. Meth. A 457 (2001) 151 Construction and analysis of anomaly-free supersymmetric [98] Dantzig, R. van; ANTARES collaboration SO(2N)/U(N) σ-models ANTARES, Physics potential, progress and status Nucl. Phys. B 594 (2001) 441-476

94 [111] Hakobyan, R. [124] Kluit, P.M. Comparison of the pion emission function in hadron-hadron Rare B decays at LEP and heavy ion collisions Nucl. Instr. Meth. A 462 (2001) 108-110 th Proc. 30 Int. Symposium on Multiparticle Dynamics, [125] Kluit, R; Timmer, P.; Schipper, J.D.; Gromov, V.; Haas, Ed. R. Csörg˝o, S. Hegyi and W. Kittel (World Scientific, A. de Singapore, 2001) p.331 Design of ladder EndCap electronics for the ALICE ITS [112] Hegyi, S.; Kittel, W. SSD From e+e− to heavy ion collisions Proc. Seventh workshop on electronics for LHC experi- Ed. T. Csörg˝o, Proc. Multiparticle Dynamics, ISMD ments (2001) 47-51 2000, October 9-15, 2000, Published in Singapore World [126] Koffeman, E.N. Scientific (2001) 639 p The construction of the ZEUS micro vertex detector [113] Hommels, B. Nucl. Instr. Meth. A 473 (2001) 26-30 The LHCb outer tracker [127] Kozlov, A. (et al.);Templon,J.A. Nucl. Instr. Meth. A 462 (2001) 278-284 The longitudinal and transverse response of the 4He(e,e’p) reaction in the dip region [114] Hulsbergen, W. Nucl. Phys. A 684 (2001) 460C-463C Status of the HERA-B experiment Acta Phys. Pol. B32(2001) 1791-1808 [128] Kramer, G.J.; Blok, H.P.; Lapikás, L.; Aconsistent analysis of(e,e’p)and (d,3He) experiments [115] Iodice, M. (et al.);Groep,D.L.;Jans, E.; Lapikás, L.; Nucl. Phys. A 679 (2001) 267-286 Hesselink, W.H.A. C.J.G. Onderwater, R. Starink [129] Laenen, E. (et al.) High missing-energy and angular dependence studies of Combined recoil and threshold resummation for hard scat- the reaction 16O(e,e’p) tering cross sections Proc. Fifth workshop on Electromagnetically Induced Proc. 30th Int. Conf. on High EnergyPhysics,World Two-Hadron Emission, June 13-16, 2001, Lund, Sweden Scientific, Osaka, Japan, 2000; 2 vol. 551-3 vol.1 [116] Jans, E.; Groep, D.L.; Hesselink, W.H.A. [130] Laenen, E.; Sterman, G.; Vogelsang, W. What can one learn from 3He(e,e’pp)n about correlations Recoil and threshold corrections in short-distance cross- and currents inthethree-nucelon system? sections Proc.Fifth Workshop on Electromagnetically Induced Phys. Rev. D63(2001) 114018 Two-Hadron Emission, June 13-16, 2001, Lund, Sweden [131] Laenen, E.; Sterman, G.; Vogelsang, W. [117] Jong, P. de Power corrections in eikonal cross-sections Colour reconnection in W decays Proc. 30th Int. Conf. on High-Energy Physics, World Proc. 30th Int. Conf. on High EnergyPhysics,World Scientific, Osaka, Japan, 2000; vol. 2:1411-1413 Scientific, Osaka, Japan, 2000; 2 vol. 694-7 vol.1 [132] Leeuwe, J.J. van; Hesselink, W.H.A.; Jans, E.; Kasdorp, [118] Kerner, R. (et al.);Holten,J.W.van W.J.; Onderwater, C.J.G.; Pellegrino, A.R. Templon, J.A. Geodesic deviation in Kaluza-Klein theories The 4He(e, e’p) cross section at high missing energies Phys. Rev. D63(2001) 027502 Phys. Lett. B 523 (2001) 6-12 [119] Kerner, R.; Holten, J.W. van; Colistete, R. Jr. [133] Liyanage, N. (et al.);Templon,J.A. 16 Relativistic epicycles: Another approach to geodesic devi- Dynamics of the O(e,e’p) reaction at high missing en- ations ergies Class. Quantum Grav. 18 (2001) 4725-4742 Phys. Rev.Lett. 86 (2001) 5670-5674 [134] Mangeol, D.J. [120] Kidonakis, N. (et al.);Laenen, E. Moments of the charged-particle multiplicity distribution Sudakov resummation and finite order expansions of heavy in Z decays at LEP quark hadroproduction cross-sections Proc. 30th Int. Symposium on Multiparticle Dynamics, Phys. Rev. D64(2001) 114001 Ed. R. Csörg˝o, S. Hegyi and W. Kittel (World Scientific, [121] Kittel, W. Singapore, 2001) p.312 Bose-Einstein correlations in Z fragmentation and other [135] Matorras, F.; Reid, D.W. reactions Measurement ofthetautopological branching ratios Proc. XLI Cracow School of Theoretical Physics, Za- Nucl. Phys. B(Proc.Suppl.) 98 (2001) 191-200 kopane, Polen, Ed. A. Bialas, M.A. Nowak and M. Sadzikowski (Jagellonian University, Cracow, 2001) [136] De Meyer, G. (et al.);Aschenauer, E.C.; Blok, H.P.; Acta Phys. Pol. B32(2001) 3927 Groep, D.; Hicks, K.; Jans, E.; Lapikás, L.; Nooren, G.J.L.; Onderwater, C.J.G.; Schipper,J.D.; Steijger, J.J.M.; [122] Kittel, W. Steenbakkers, M.F.M.; Steenhoven, G. van der; Uden, + − Interconnection Effects and W W Decays M.A. van; Volmer, J. th Proc. XXXIV Rencontres de Moriond, ’99 QCD and Alpha-cluster knockout in the 16O(e,e’α)12Creaction High Energy Hadronic Interactions, Ed. J. Tran Thanh Phys. Lett. B 513 (2001) 258-264 Van (The Gioi Publishers, Vietnam, 2001) p.71 [137] Moch, S.; Vermaseren, J.A.M.; Vogt, A. [123] Kjaer, N;Mulders, M Next-to-next-to leading order QCD corrections to the pho- Mixed Lorentz Boosted Z0’s ton’s parton structure CERN-OPEN/2001-026 (2001) Nucl. Phys. B 621 (2002) 413-458

95 [138] Nagorny, S. [152] Snoeys, W. (et al.);San Segundo Bello, D. Comment on “Radiative proton-deuteron capture in a Pixel readout electronics development for theALICEpixel gauge invariant relativistic model” vertex and LHCbRICHdetector Phys. Rev. C63(2001) 019801 Nucl. Instr. Meth. A 465 (2001) 176-189 [139] Nikolenko, D.M. (et al.);Jager,C.W.de;Vries,H.de [153] Steenhoven, G. van der; HERMES collaboration Measurement of polarization observables in elastic and in- Nuclear effects in R = σL/σT in DIS elastic electron deuteron scattering at the VEPP-3 storage Proc. DIS 2000 Ed. by J.A. Gracey, T. Greenshaw. 124- ring 125 th Proc. 16 Int. Conf. on Few-BodyProblemsinPhysics [154] Steenhoven, G. van der (FB 16), Taipei, Taiwan, China, 6-10 Mar. 2000 De nieuwe kernfysica : een spel van quarks en gluonen Nucl. Phys. A 684 (2001) 525-527 Ned. T. Nat. 67 (2001) 322-325 [140] Nyawelo, T.S.; Holten, J.W. van; Groot Nibbelink, S. [155] Steenhoven, G. van der; HERMES Collaboration Superhydrodynamics Hard Exclusive Processes at HERMES Phys. Rev. D64(2001) 021701 Proc. Eighth Conf. on Mesons and Light Nuclei, Prague, [141] Oldeman, R.G.C. Czech Republic, July 2-6, 2001, Ed. J. Adam, P. By- Measurement of differential neutrino-nucleon cross-sections dzovsky and J. Mares, AIP Conference Proceedings 603 and structure functions using the CHORUS lead calorime- (2001) 161 ter [156] Steenhoven, G. van der Proc. 30th Int. Conf. on High EnergyPhysics,World HERMES: first observation of Compton scattering at the Scientific, Osaka, Japan, 2000; 2 vol. 516-8 vol.1 quark level [142] Phaf, L.; Weinzierl, S. Nucl. Phys. News Int. 11,No. 4 (2001) 30 Dipole formalism with heavy fermions [157] Steenhoven, G. van der J. High Energy Phys. 04 (2001) 006 Retirement and policy making at NIKHEF - a symposium [143] Reid, D.W. Nucl. Phys. News Int. 11,No. 4 (2001) 32 Review of the neutral current [158] Timmermans, C. Nucl. Phys. B(Proc.Suppl.) 98 (2001) 105-114 Onderzoek naar kosmische muonen met de L3 detector In jaarboek 2000, Vereniging van Akademie-onderzoekers [144] Reinhold, J. (et al.);Volmer,J.;Zihlman,B.) “Over de grenzen van het weten”, Amsterdam, 2001, p.83 Electroproduction of kaons and light hypernuclei Nucl. Phys. A 684 (2001) 1 [159] Tuning, N.; ZEUS collaboration Measurement of F and xF structurefunctions with the [145] Retey, A.; Vermaseren, J.A.M. 2 3 ZEUS detector Some higher moments of deep inelastic structure functions Proc. DIS 2000, Ed. by J.A. Gracey, T. Greenshaw. 87-89 at next-to-next-to-leading order of perturbative QCD Nucl. Phys. B 604 (2001) 281-311 [160] Virgili, T.; Antinori, F. (et al.);Botje,M.;Haas,A.P.de; Kamermans, R.; Kuijer, P.G.; Schillings, E.; Brink, A. van [146] San Segundo Bello, D.; Visschers, J. den; Ven, P. van de; Eijndhoven, N. van Design of pixel-level ADC’s for energy sensitive hybrid Study of the production of strange and multi-strange par- pixel detectors ticles in lead-lead interactions at the CERN SPS: the Proc. IEEE Nuclear Science Symposium and Medical NA57 experiment Imaging Conf., Lyon, France, 15-20 Oct. 2000. h9.98- Nucl. Phys. A 681 (2001) 165C-173C 100 [161] Volmer J.; Blok, H.P. [147] San Segundo Bello, D.; Nauta, B.; Visschers, J. Measurement ofthechargedpion electromagnetic form Design of analog-to-digital converters for energy-sensitive factor hybrid pixel detector Phys. Rev.Lett. 86 (2001) 1713-1716 Nucl. Instr. Meth. A 466 (2001) 218-225 [162] Weinzierl, S.; Yakovlev, O. [148] Schellekens, A.N.; Sousa, N. New approach for calculating heavy-to-light form factors Open descendants of U(2N) orbifolds at rational radii with QCD sum rules on the light-cone Int. J. Mod. Phys. A16(2001) 3659-3671 J. High Energy Phys. 01 (2001) 005 [149] Schellekens, A.N.; Stanev, Ya.S. [163] White, V. (et al.);Bos,K.;Leeuwen,W.van Traceformulasfor annuli The D0 Data Handling System J. High Energy Phys. (2001) 0112:012 Proc. Int. Conf. on Computing in High Energy and [150] Schulte, E.C. (et al.);Blok,H.P.;Zihlman, B. Nuclear Physics, Ed. H.S. Chen, Beijing, China, 3-7 Sept. Measurement of the High Energy Two-Body Deuteron 2001, p20 Photodisintegration Differential Cross Section Phys. Rev.Lett. 87 (2001) 102302 [151] Snoeys, W. (et al.);San Segundo Bello, D. Pixel readout chips in deep submicron CMOS for ALICE and LHCb tolerant to 10 Mrad and beyond Nucl. Instr. Meth. A 466 (2001) 366-375

96 2PhDTheses

[1] Mil, A. van Cosmic-Ray Muons in the L3 Detector Katholieke Universiteit Nijmegen, January 2001 [2]Batenburg, Marinus Franciscus van Deeply-bound protons in 208Pb Universiteit Utrecht, March 2001 [3] Melzer, Oliver Study of charm production by neutrinos in nuclear emulsion Universiteit van Amsterdam, April 2001 [4] Harvey, Mark Inclusive scattering of electrons from polarized 3He Hampton University, May 2001 [5] Ven,Peter van de Centrality Dependence of Λ Production in Pb-Pb Colli- sions Universiteit Utrecht, May 2001 [6] Muijs, Alexandra Jantina Monica Tau pair production above the Z resonance Katholieke Universiteit Nijmegen, September 2001 [7] Mulders, Martijn Pieter Direct measurement of the W boson mass in e+e− collisions at LEP Universiteit van Amsterdam, September 2001 [8] Tuning, Niels Proton structure functions at HERA Universiteit van Amsterdam, September 2001 [9] Rodrigues,JoaoMiguelPereira Resina Modelling quark and gluon correlation functions Vrije Universiteit Amsterdam, October 2001 [10] Sichtermann, Ernst Paul The nucleon structure fuction g1 from deep-inelastic muon scattering Vrije Universiteit Amsterdam, October 2001 [11] Gulik, Robert Christiaan Wilhelmus van Resonance production in two-photon collisions Universiteit Leiden, November 2001 [12] Agasi, Erwin Kaon prodution in τ-decays Universiteit van Amsterdam, December 2001

97 3InvitedTalks

[1] M. van den Akker [16] N.J.A.M. van Eijndhoven Looking for Gamma-Ray sources using the L3+Cosmics From Woodblock to Expanding Universe experiment at CERN Invited evening lecture, Kiwanis Utrecht, November 20, NNV najaarsvergadering, Lunteren, October 26, 2001 2001. [2] M. Botje [17] N.J.A.M. van Eijndhoven Error Estimates on Parton Density Distritubions In the Light of the Quark-Gluon Plasma : A Thermometer New Trends in Hera Physics 2001, Ringberg Castle, Te- in the Big Bang gernsee (Germany), June 17-22, 2001. Astrophysics department Utrecht, December 3, 2001. [3] J.F.J. van den Brand and M. Merk [18] N.J.A.M. van Eijndhoven Topical Lectures on Discrete Symmetries The Quest for the Quark Soup NIKHEF, Amsterdam, June 14, 2001 Third North West Europe Nuclear Physics Conf., Bergen [4] M. Bruinsma (Norway), April, 2001 Charmonium physics at Hera-B [19] J.J. Engelen Hard Probe Collaboration meeting, NBI, Copenhagen (Den- ep Scattering at 300 GeV mark), May 18, 2001. Colloquium, KVI Groningen, October 16, 2001 [5] M. Bruinsma [20] J.J. Engelen Quarkonium suppression at Hera-B De detectie van kosmische neutrino’s Seminar, CERN Heavy Ion Forum, CERN, Geneva (Swit- Koninklijk Natuurkundig Gezelschap, Groningen, October serland), July 5, 2001. 16, 2001 [6] H.J. Bulten [21] J.J. Engelen Distributed Computing and LHCb Antares: een detector voor kosmische neutrino’s NIKHEF, Amsterdam, June 26, 2001 Diligentia, Den Haag, September 24, 2001 [7] J. van Dalen Bose-Einstein correlations in WW events at LEP [22] J.J. Engelen XXXIst Int. Symposium on Multiparticle Dynamics (ISMD Status of the LHC Experimental Programme 2001), Datong (China), September 1-7, 2001 7th WorkshoponElectronicsforLHCExperiments,Stock- holm (Sweden), September 2001 [8] J. van Dalen Bose-Einstein correlations: the only known tool to obtain [23] T.O. Eynck information about the space-time structure of the hadron Resummation and polarized heavy quark production source from the measured particle momenta Natl. Theoretical Physics Seminar, NIKHEF Amsterdam, Hua-Zhong Normal University, Wuhan, (China), Septem- October 12, 2001 ber 13, 2001 [24] T.O. Eynck [9] J. van Dalen Comparison of phase space slicing and dipole subtraction Bose-Einstein correlations in e+e− events at LEP methods Hua-Zhong Normal University, Wuhan (China), Septem- NNV najaarsvergadering, Lunteren, October 2001 ber 14, 2001 [25] R. Hart [10] J. van Dalen Communication between Trigger/DAQ and DCS in AT- Bose-Einstein correlations in WW events at LEP LAS NNV najaarsvergadering, Lunteren, October 26, 2001 CHEP01, Beijing (China), September 2001 [11] M. Dierckxsens [26] E. Garutti Resonance Production in gamma-gamma collisions at L3 Fisica dello spin ad HERMES EPS Conf. Budapest (Hungary), July 12-18, 2001 Lecture at the University of Ferrara, Ferrara (Italy), May [12] A. Doubi 26, 2001 Magnetic Monopoles Search with the ANTARES detector [27] E. Garutti HEFIN Colloquium, June 7, 2001 Hadron Formation in Nuclei in Deep-Inelastic Scattering [13] S. Duensing NNV najaarsvergadering, Lunteren, The Netherlands, Oc- Tau identiﬁcation at D0 tober 26, 2001 NNV najaarsvergadering, Lunteren, October 26, 2001 [28] E. Garutti [14] N.J.A.M. van Eijndhoven Physics at HERMES (an experiment to study the struc- Heavy-Ion Physics at CERN: From SPS to the ALICE LHC ture function of the nucleon) experiment ZEUS PhD Colloquia, DESY, Hamburg (Germany), De- Physics colloquium University of Bergen, Bergen (Nor- cember 1, 2001 way), April 18, 2001. [29] F. Hartjes [15] N.J.A.M. van Eijndhoven Diamond as a Detector for High Energetic Particles Physics Aspects of Heavy-Ion Collisions University of Florence, Florence (Italy), November 23, Physics colloquium, Nikhef Amsterdam, October 19,2001. 2001

98 [30] J.W. vanHolten [45] S.J. de Jong Worldline deviations and epicycles The TESLA project Journees Relativistes, Dublin (Ireland), September 2001 Hua-Zhong Normal University, Wuhan (China), June 20, [31] J.W. vanHolten 2001 Aspects of BRST-Quantization [46] W. Kittel Lectures at the summerschool “Geometry and Topology Introductory review of correlations and fluctuations in Physics” Rot a/d Rot (Germany), September 2001 XXXIst Int. Symposium on Multiparticle Dynamics (ISMD [32] Y. Hu 2001), Datong (China), September 1-7, 2001 + − Searches of the Standard Model Higgs Boson in e e [47] W. Kittel collisions with the L3 detector at LEP Review of experimental constraints on Bose-Einstein mod- HEFIN Colloquium, February 8, 2001 elling [33] Y. Hu WW Physics Workshop, Cetraro (Italy), October 12-17, Searches for the SM Higgs boson with leptons in the final 2001 state with L3 detector at LEP [48] W. Kittel NNV najaarsvergadering, Lunteren, October 26, 2001 − Correlations in e+e collisions [34] L. Huiszoon Symposium in Honor of N. Antoniou, Univ. of Athens The Geometry of WZW Orientifolds (Greece), November 9, 2001 Univ. of Rome ‘Tor Vergata’, Rome (Italy), December 3, [49] W. Kittel 2001 Correlations in e+e−,hpand AA collisions [35] L. Huiszoon Winterschool on Heavy Ion Physics, Budapest, (Hungary), The Geometry of WZW Orientifolds December 5-7, 2001 RUG, Groningen, December 11, 2001 [50] W. Kittel [36] W. Hulsbergen Introduction to correlations and fluctuations Status of the Hera-B Experiment IPP Workshop onMultiparticle Production in QCD Jets, Cracow Epiphaniy Conf on b-Physics and CP violation, Durham (UK), December 12-15, 2001 Cracow (Poland), January 5-7, 2001 [51] P.M. Kluit [37] E. Jans B oscillations What can one learn from 3He(e,e’pp)n about correlations s Int. Conf. on FlavorPhysics(ICPF2001), Zhang-Jia-Jie and currents inthethree-nucelon system? (China) Fifth Workshop on ”Electromagnetically induced Two- Hadron Emission”, Lund (Sweden), June 13-16, 2001 [52] E. Laenen [38] S.J. de Jong The strong interaction IT uses and developments in Experimental High Energy Lectures at the University of Iceland (Reykjavik), April Physics 2001 CSI Colloquium, KUN, Nijmegen, February 12, 2001 [53] E. Laenen [39] S.J. de Jong Resummation in QCD and summary talk TheTevatron: Hadron collider physics LesHouches workshop on Physics at TeV Colliders, Les Hua-Zhong Normal University, Wuhan (China), June 13, Houches (France), May 2001 2001 [54] E. Laenen [40] S.J. de Jong Opportunities in Heavy Flavour Physics with HERA II D0: Run 1 results DESY, Hamburg (Germany), July 2001 Hua-Zhong Normal University, Wuhan (China), June 14, [55] E. Laenen 2001 Heavy Flavour Production at HERA [41] S.J. de Jong Bonn University, Bonn (Germany), July 2001 D0: Run 2 prospects [56] E. Laenen Wuhan central normal university, Wuhan (China), June The Standard Model and the Strong Force 14, 2001 Physics Colloquium, RUG (Groningen), September 2001 [42] S.J. de Jong Standard Model Higgs [57] E. Laenen Hua-Zhong Normal University, Wuhan (China), June 15, Threshold Effects in Heavy Quark Production 2001 Torino University, Torino (Italy), October 2001 [43] S.J. de Jong [58] L. Lapikás Non-SM Higgses and SUSY Radiative corrections in A(e,e’) Hua-Zhong Normal University, Wuhan (China), June 18, Workshop on Radiative Corrections, Hamburg (Germany), 2001 February 2, 2001 [44] S.J. de Jong [59] L. Lapikás Semiconductor tracking detector techniques Rescattering and the 208Pb(e,e’p) reaction Hua-Zhong Normal University, Wuhan (China), June 19, Miniworkshop on Rescattering, Tübingen (Germany), Oc- 2001 tober 22, 2001

99 [60] W. Lavrijsen [76] M.C. Simani COmBined muon Reconstruction for Atlas Spin physics at HERMES Atlas Software Workshop, Frascati (Italy), May 16, 2001 Advanced study institute: symmetries and spin, Int. school- workshop ’Prague-Spin-2001’, Prague (Czech Republic), [61] W. Lavrijsen July 15-28, 2001 COmBined muon Reconstruction for Atlas Atlas Physics Workshop, Lund (Sweden), September 13, [77] N. Sousa 2001 Recent advances in string theory Univ. Coimbra, Coimbra (Portugal), January 5, 2001 [62] W. Lavrijsen ComBined muon reconstruction for Atlas [78] G. van der Steenhoven NNV najaarsvergadering, Lunteren, October 26, 2001 Skewed Parton Distributions at HERMES, ELFE and TESLA- N [63] W.J. Metzger Workshop on ”Skewed Parton Distributions”, European New Bose-Einstein results from L3 ESOP RTM network, Orsay (France), January 18, 2001 XXXIst Int. Symposium on Multiparticle Dynamics (ISMD 2001), Datong (China), September 1-7, 2001 [79] G. van der Steenhoven Deep-inelastic scattering on nuclei [64] W.J. Metzger Workshop on “Correlations in nucleons and nuclei”, In- Tuning QCD Monte Carlo programs in L3 stitute for NuclearTheory(INT),Seattle, Washington WW Physics Workshop, Cetraro (Italy), October 15, 2001 (USA), March 19, 2001 [65] W.J. Metzger [80] G. van der Steenhoven FSI Outlook The role of the nucleus in (polarized) deep-inelastic scat- WW Physics Workshop, Cetraro (Italy), October 17, 2001 tering [66] W.J. Metzger Third North West Europe Nuclear Physics Conf., Bergen Rapidity Gaps and Colour (Re-)Connection (Norway), April 18, 2001 IPP Workshop onMultiparticle Production in QCD Jets, [81] G. van der Steenhoven Durham (UK), December 14, 2001 De nieuwe kernfysica: een spel van quarks en gluonen [67] V. Mexner Inaugurele rede, Rijksuniversiteit Groningen, Groningen, Spin-asymmetry of photo-produced high-pT hadron pairs June 5, 2001 in HERMES [82] G. van der Steenhoven NNV najaarsvergadering, Lunteren, The Netherlands, Oc- Introduction tober 26th, 2001 Symposium ter gelegenheid van het afscheid van prof. dr. [68] N.A. Naumann Ger van Middelkoop als directeur van NIKHEF: “Past and HEP Particle Classes in ROOT future policies on facilities for nuclear and high energy ROOT2001, Int. HENP ROOT Users Workshop, Fermi- physics research”, Amsterdam, 22 June 2001 lab, Batavia Ill. (USA), June 14, 2001 [83] G. van der Steenhoven [69] T.S. Nyawelo Hard Exclusive Processes at HERMES Supersymmetric hydrodynamics Eighth Conf. on Mesons and Light Nuclei, Prague, (Czech Inst. Theor. Physics RUG (Groningen), November 30, Republic), July 4, 2001 2001 [84] G. van der Steenhoven [70] M.P. Sanders Spin Physics: where will we be in 2006? Measurement of Bose-Einstein correlations between neu- IPPP Workshop on Future Physics at HERA, Durham tral (and charged) pions from hadronic Z decays (UK), December 6-7, 2001 University of Manchester, Manchester (UK), March, 2001 [85] J.A.M. Vermaseren [71] M. Sanders How to compute three-loop QCD structure functions Bose-Einstein correlations of neutral and charged pions in University of Helsinki, Helsinki (Finland), March 2001 hadronic Z decays [86] J.A.M. Vermaseren NNV najaarsvergadering, Lunteren, October 26, 2001 Modern Computer Algebra [72] A.N. Schellekens Symposium in honour of prof. dr. M. Veltman, University Open ends in string theory of Amsterdam, May 2001 Univ. of Rome ‘Tor Vergata’, Rome (Italy), April 4, 2001 [87] J.A.M. Vermaseren [73] A.N. Schellekens Ingredients of a three-loop structure functin calculation Open ends in string theory University of Tokyo, Tokyo (Japan), November 2001 Univ. di Firenze, Florence (Italy), April 16, 2001 [88] J. Visser [74] A.N. Schellekens Nuclear Eﬀects in Deep Inelastic Scattering Open ends in string theory Workshop on Perspectives in Hadronic Physics, Trieste Univ. di Genova, Genua (Italy), April 23, 2001 (Italy), May 7-11, 2001 [75] A.N. Schellekens [89] H. Wilkens Open ends in string theory Preliminary results from L3+Cosmics Vrije Univ. Amsterdam, May 23, 2001 NNV najaarsvergadering, Lunteren, October 26, 2001

100 [90] B. Wijngaarden b-Tagging at D0 NNV najaarsvergadering, Lunteren, October 26, 2001 [91] B. Zihlmann Nuclear Eﬀects on R = σL/σT in Deep Inelastic Scatter- ing Department of Physics, University of Basel, Basel (Switzer- land), June 7, 2001

101 4Seminars at NIKHEF

[1] January 19, 2001 [18] March 26, 2001 M. Mulders J. Templon The Art of W mass reconstruction in Delphi Few-Body Nuclear Physics at Jefferson Lab [2] January 23, 2001 [19] March 30, 2001 D. Reid J. Ralston The Lorentz structure of τ decays The Case for Zero Spin of the Gauge Sector [3] January 24, 2001 [20] April 12, 2001 S. Soldner-Rembold M. Amarian The Hunt for the Higgs Boson at LEP Deeply Virual Compton Scattering and Exclusive Meson [4] January 29, 2001 Production at Hermes M. Vreeswijk [21] April 26, 2001 The Making of Atlas Muon Chambers and the World Wide E. do Couto e Silva HiggsHunt Particle Astrophysics at SLAC [5] February 1, 2001 [22] May 11, 2001 F. Sanchez F.E. Close HERA B: an experiment to measure CP violation Glueballs: A central mystery [6] February 2, 2001 D. Zer Zion [23] May 15, 2001 Non Standard Model Higgs searches at LEP Chr. Korthals Altes Extra compact dimensions, or how to avoid domain walls [7] February 5, 2001 C. Padilla [24] May 18, 2001 CP violation and HERA-B: experiences for future experi- J. Harris ments First Glimpses of the Primordial Quark Gluon Soup? [8] February 5, 2001 [25] June 1, 2001 R. Nisius H. Stroeher The Structure of the Photon Hadron physics at COSY/Jülich [9] February 7, 2001 [26] June 6, 2001 U. Uwer W. Giele HERA-B, a Spectrometer for High Rates: Achievements Parton DensityFunction Uncertainties and Prospects [27] June 8, 2001 [10] February 21, 2001 J. Dainton A. Pellegrino Experimental Quantum Chromodiffraction Inclusive Deep Inelastic Scattering Studies at HERA [28] June 27, 2001 [11] February 23, 2001 Y. Gouz C. Tully Luminosity measurements in DELPHI with the STIC de- The Higgs search at LEP tector [12] March1,2001 [29] June 27, 2001 G. Raven H.J. Bulten 0 − ¯0 Measurement of CP violating Asymmetries and B B Physics and Computing at LHCb Mixing at Babar [30] June 29, 2001 [13] March1,2001 R. Vogt P. Gorham Charmonium production at HERA B Extreme Astronomy : Neutrinos from the edge [14] March9,2001 [31] June 29, 2001 A. de Roeck M. Bouwhuis The physics potential of CLIC Recent results from Hermes [15] March 12, 2001 [32] August 31, 2001 T. Azemoon H. Chang (FOM) TheL3Simulation Facility Accenten voor 2001/2002 [16] March 12, 2001 [33] September 7, 2001 Ch. Loomis R. Oldeman Visualization of High-Energy Physics B-physics at CDF: status and prospects [17] March 23, 2001 [34] September 14, 2001 O. Melzer R. Yoshida Charm production at CHORUS Hard QCD and Structure Functions

102 [35] September 21, 2001 E. Richter-Was Higgs bosons at LHC [36] September 28, 2001 F. J. Yndurain NNLO evaluations of DIS and precision calculations of α-strong [37] October5,2001 N. de Groot From Pixels to Physics [38] October18,2001 E. Leader First ever extraction of Fragmentation Functions without assumptionsconcerningfavoured/unfavoured transitions [39] October19,2001 N. vanEijndhoven Heavy Ion Physics [40] November 2, 2001 D. Cassel Recent results from CLEO and plans for CLEO-c [41] November 9, 2001 P. Kluit Status of the CKM matrix; impact of LEP [42] November 16, 2001 P. Katgert Recent evidence for an acceleration of the expansion of the Universe [43] November 30, 2001 J. Walraven Properties of the Bose Einstein Condensates [44] December 7, 2001 G. Raven CP violation at Babar

103 5NIKHEF Annual Scientiﬁc Meeting December 13-14, 2001, Amsterdam [1] A. Bacchetta [15] E. Koﬀeman ATransverse Look at the Proton Developments in vertex detection [2] T. Bauer [16] P. Kuijer Overview of the B-physics program Status of the Alice program [3] W. Beenakker [17] M. van Leeuwen Large electroweak corrections at TeV-scale linear colliders Status of NA49 [4] S. Bentvelsen [18] F. Linde ATLAS software ATLAS progress report [5] M. Bruinsma [19] F. Linde Recent results from HERA-B Recent ECFA and HEPAP reports [6] M. Dierckxsens [20] S. Peeters Wselection/cross section/Anom. couplings at LEP ATLAS tracker [7] S. Duensing [21] E. van der Pijll D0 analysis report Direct photons at WA98 [8] J.J. Engelen [22] M.C. Simani NIKHEF: today and tomorrow Flavour decomposition of the nucleon spin [9] J. Ferreira Montenegro [23] F. Spada Wmassmeasurement at LEP neutrino-charm physics [10] F. Filthaut [24] J. Templon D0 running report The EU DataGrid Project at NIKHEF [11] S. Grijpink [25] H. Tiecke Charged Current interactions Status ZEUS [12] L. Huiszoon [26] C. Timmermans D-branes and O-planes in String Theory Cosmic ray physics with the L3 muon spectrometer [13] R. Hierck [27] G. de Vries Track reconstruction at LHCb Gamma Ray Burst detection with the Antares detector [14] M. de Jong Status of the Antares project

104 FResources and Personnel 1Resources

In 2001 the NIKHEF income was 39.9 Mfl. The budget The largest program, Atlas, represents about a quarter figures of the NIKHEF partners were: FOM-institute of the total budget. Antares appears for the first time 26.1 Mfl, universities 9.6 Mfl of which 3.2 Mfl through as an approved FOM-program. Capital investments in the FOM Research Division of Subatomic Physics. In 2001 were made for Atlas, LHCb and Antares. addition, third parties contributed 4.2 Mfl to the NIKHEF income. Capital investments 2001: 7.8 Mfl Total Income 2001: 39.9 Mfl

FOM institute SAF/NIKHEF FOM Research ATLAS Division SAF LHCb Universities Antares Third parties

Figure 1.1: NIKHEF funding Figure 1.3: Capital investments

Expenses 2001: 39.9 Mfl NIKHEF Personnel 11

1 2 Chorus 1 2 LEP 3 3 Zeus 102 10 4 4 Hermes 168 102 66 5 9 Atlas 6 Alice 8 7 LHCb 27 5 8 Theory technical staff 9 support staff Antares junior scientists scientific staff 7 10 Trans.prog. senior scientists 6 11 Third parties

Figure 1.4: Personnel as of December 31, 2001 (left). Subdivision of personnel: the scientists divided into se- Figure 1.2: Exploitation budget nior and junior scientists (right).

105 2Membership of Councils and Committees during 2001

NIKHEF Board HEP Board EPS F. T. M. Nieuwstadt (FOM, chairman) J. J. Engelen K. H. Chang (FOM) J. J. M. Franse (UvA) Research Board CERN S. Groenewegen (VU) J. J. Engelen (until 1 September 2001) C. W. P. M. Blom (KUN) EPAC G. Luijckx J. G. F. Veldhuis (UU) H. G. van Vuren (secretary, FOM) Beleidsadvies college KVI G. Luijckx Scientific Advisory Committee NIKHEF P. Mulders G. Goggi (CERN) K. Pretzl (Bern) from Oct. 2001 Scientific Committee Frascati Laboratory D. von Harrach (Univ. Mainz) until Oct. 2001 G. van Middelkoop G. Ross (Univ. Oxford), chair, from Oct. 2001 M. Spiro (IN2P3) Scientific Advisory Committee, Physique Nucleaire, Orsay J. Stachel (Univ. Heidelberg), chair, until Oct. 2001 P. K. A. de Witt Huberts J. Dainton (Univ. Liverpool) fromOct.2001 Scientific Advisory Committee DFG Hadronen Physik NIKHEF WorksCouncil J. H. Koch P. de Jong (chairman) P. K. A. de Witt Huberts M. Vreeswijk (2nd chairman) Program Advisory Committee, ELSA (Bonn)/MAMI (Mainz) R. Hart (1st secretary) H. P. Blok J. Hogenbirk (2nd secretary) A. Boucher Program Advisory Committee, Jefferson Laboratory J. Dokter H. P. Blok E. van Kerkhoff NNV Board R. Kluit E. W. A. Lingeman S. Schagen J. Konijn H. Schuijlenburg J. Velthuis OECD Global Science Forum Consultative Group G. van Middelkoop until 1 July 2001 FOM Board J. J. Engelen starting 1 July 2001 J. J. Engelen until 1 July 2001 S. de Jong starting 1 January 2001 Other committees SPC-CERN St. CAN : J.Vermaseren J. J. Engelen until 1 September 2001 CERN, Task Force 2 : G. van Middelkoop K. J. F. Gaemers EPCS : W.Heubers LHCC-CERN ESRF : G. Luijckx J. J. Engelen (chairman) until 1 September 2001 HTASK : K. Bos H. Tiecke (member) starting 1 September 2001 ICANN : R. Blokzijl SPSC-CERN ICHEP2002 : G. van Middelkoop (chairman) B. Koene until 1 February 2001 IRI:J.H.Koch M. de Jong IWoRID : J. Visschers Extended Scientific Council, DESY JINR Scientific Council : G. van Middelkoop K. J. F. Gaemers Kuratorium HEPHY , Vienna : E. W.Kittel J. J. Engelen NOMINET : R. Blokzijl ECFA Physical Review Letters editorial Board : G. van der Steenhoven J. J. Engelen (also in Restricted ECFA starting 1 July 2001) RIPE : R.Blokzijl K. J. F. Gaemers St. Physica Board : J. Konijn R. Kamermans WAC KVI:G.vanderSteenhoven E. W. Kittel G. van Middelkoop (also in Restricted ECFA until 1 July 2001) WCW Board : A.J.vanRijn

NuPECC G. van Middelkoop

106 3Personnel as of December 31, 2001

FOM, and the universities UVA, VU, KUN and UU are partners Gulik, Ir. R.C.W. van UL ATLAS in NIKHEF (See colofon). UL and UT denote the universites of Hartjes, Dr. F.G. FOM ATLAS Leiden and Twente. GST stands for guest. Other abbreviations Heesbeen, Drs. D. FOM HERMES refer to the experiments, projects and departments. Heijboer, Drs. A.J. UVA ANTARES Hesselink, Dr. W.H.A. VU HERMES 1. Experimental Physicists Hessey, Dr. N.P. FOM ATLAS Hierck, Drs. R.H. FOM-VU B-Phys. Akker, Drs. M. van den KUN L-3 Hommels, Ir. L.B.A. FOM B-Phys. Apeldoorn, Dr. G.W. van UVA B-Phys. Hu, Drs. Y. FOM-KUN L-3 Baak, Drs. M. VU B-Phys. Hulsbergen, Drs. W.D. FOM B-Phys. Bakel, Drs. N.A. van FOM B-Phys. Jans, Dr. E. FOM AmPS-Phys. Baldew, Drs. S.V. UVA L-3 Jong, Dr. M. de FOM ANTARES Balm, Drs. P.W. FOM ATLAS Jong, Dr. P.J. FOM ATLAS Barisonzi, Drs. M. UT ATLAS Jong, Prof.Dr. S.J. KUN ATLAS Barneo González, Drs. P.J. FOM Other Projects Kamermans, Prof.Dr. R. FOM-UU ALICE Bauer, Dr. T.S. FOM B-Phys. Ketel, Dr. T.J. FOM-VU B-Phys. Bentvelsen, Dr. S.C.M. FOM ATLAS Kittel, Prof.Dr. E.W. KUN L-3 Blekman, Drs.Mw. F. FOM ATLAS Klok, Drs. P.F. FOM-KUN ATLAS Blok, Dr. H.P. VU HERMES. Klous, Drs. S. FOM-VU B-Phys. Blom, Drs. H.M. FOM DELPHI Kluit, Dr. P.M. FOM ATLAS Blouw, Dr. J. Other HERMES Koene, Dr. B.K.S. FOM B-Phys. Bobbink, Dr. G.J. FOM L-3 Koffeman, Dr.Ir. Mw. E.N. FOM ZEUS Boer, Dr. F.W.N. de GST ALGEMEEN König, Dr. A.C. KUN ATLAS Boersma, Drs. D.J. GST AmPS-Phys. Konijn, Dr.Ir. J. GST CHORUS Bokel, Drs. C.H. GST ZEUS Kooijman, Prof.Dr. P.M. UVA ZEUS Bos, Dr. K. FOM ATLAS Kuijer, Dr. P.G. FOM ALICE Botje, Dr. M.A.J. FOM ALICE Laan, Dr. J.B. van der FOM Other Projects Bouwhuis, Drs. Mw. M.C. FOM ANTARES Lapikás, Dr. L. FOM HERMES Brand, Prof.Dr. J.F.J. vanden VU OtherProjects Lavrijsen, Drs. W.T.L.P. FOM-KUN ATLAS Bruinsma, Drs. M. FOM B-Phys. Laziev, Drs. A.E. FOM-VU HERMES Bruinsma, Ir. P.J.T. GST ANTARES Leeuwen, Drs. M. van FOM ALICE Buis, Drs. E.J. GST ATLAS Linde, Prof.Dr. F.L. UVA ATLAS Bulten, Dr. H.J. FOM-VU B-Phys. Luijckx, Ir. G. FOM ATLAS Buuren, Drs. L.D. van FOM Other Projects Maas, Dr. R. FOM Other Projects Calvet, Dr. D. GST ATLAS Maddox, Drs. E. UVA ZEUS Cârloganu, Dr. Mw. F.C. FOM ANTARES Mangeol, Drs. D GST L-3 Crijns, Dipl.Phys.F.J.G.H. FOM-KUN ATLAS Massaro, Dr. G.G.G. FOM ATLAS Dalen, Drs. J. van FOM-KUN L-3 Merk, Dr. M.H.M. FOM B-Phys. Dam, Dr. P.H.A. van UVA DELPHI Metzger, Dr. W.J. KUN L-3 Dantzig, Dr. R. van GST CHORUS Mevius, Drs. Mw. M. FOM-UU B-Phys. Daum, Prof.Dr. C. GST ATLAS Mexner, Drs. Mw. I.V. FOM-BR HERMES Diddens, Prof.Dr. A.N. GST DELPHI Middelkoop, Prof.Dr. G. van GST Other Projects Dierckxsens, Drs. M.E.T. FOM L-3 Naumann, Drs. A. FOM ATLAS Dierendonck, Drs. D.N. van GST L-3 Needham, Dr. M.D. FOM B-Phys. Duensing, Drs. Mw. S. KUN ATLAS Nooren, Dr.Ir. G.J.L. FOM-UU ALICE Duinker, Prof.Dr. P. GST L-3 Ouchrif, Dr. M. FOM B-Phys. Eijk, Prof.Dr. B.van FOM ATLAS Peeters, Ir. S.J.M. FOM ATLAS Eijk, Ir. R.M. van der FOM B-Phys. Pellegrino, Dr. A. FOM B-Phys Eldik, Drs. J.E. van GST DELPHI Peters, Drs. O. UVA ATLAS Engelen, Prof.Dr. J.J. UVA DIR Petersen,Drs.B. GST L-3 Erné, Prof.Dr.Ir F.C. GST L-3 Phaf, Drs. L.K. FOM ATLAS Eyndhoven, Dr. N. van FOM-UU Other Projects Pijll, Drs. E.C. van der FOM-UU Other Projects Ferreira Montenegro, Drs. Mw. J. FOM DELPHI Putte, Dr.Ir. M.J.J. van den FOM Other Projects Filthaut, Dr. F. KUN ATLAS Reid, Dr. D.W. FOM DELPHI Fornaini,Drs.A. FOM ATLAS Garutti, Drs. Mw. E. FOM HERMES Gouz, Dr. I GST B-Phys. Graaf, Dr.Ir. H. van der FOM ATLAS Grijpink, Drs. S.J.L.A. FOM ZEUS Groep, Dr. D.L. FOM Other Projects

107 Reischl, Drs. A.J. FOM HERMES Iersel, Drs. M. van FOM-VU Rens, Drs. B.A.P. van FOM ANTARES Kleiss, Prof.Dr. R.H.P. KUN Rijke, Drs. P. de FOM-UU ALICE Koch, Prof.Dr. J.H. FOM Roux, Drs. Mw. B. FOM-KUN L-3 Laenen, Dr. E. FOM San Segundo Bello, Drs. D. FOM-HCM Other Projects Marques de Sousa, Drs. N.M. GST Sanders, Drs. M. GST L-3 Metz, Dr. A. FOM-VU Sbrizzi, Drs. A. FOM B-Phys. Mulders, Prof.Dr. P.J.G. VU Schagen, Drs. S.E.S. FOM ZEUS Nyawelo, B.Sc. T.S. FOM Schillings, Drs. E. FOM-UU ALICE Pijlman, Drs. F. VU Scholte, Ir. R.C. UT ATLAS Riccioni, Dr. F. FOM Schotanus, Dr. D. J. KUN L-3 Schellekens, Prof.Dr. A.N.J.J. FOM Simani, Drs. Mw. M.C. FOM-VU HERMES Veltman, Prof.Dr. M.J.G. GST Sokolov, Drs. A. UU ALICE Vermaseren, Dr. J.A.M. FOM Spada, Dr. Mw. F.R. GST CHORUS Vogt, Dr. A. Other Steenbakkers, Drs. M.F.M. GST Other Projects Warringa, Drs. H. VU Steenhoven, Prof.Dr. G. van der FOM HERMES Wit, Prof.Dr. B.Q.P.J. de UU Steijger, Dr. J.J.M. FOM HERMES Zhou, Dr. M. FOM Stonjek, Dipl. Phys. S. Other ZEUS Tassi, Dr. E. FOM ZEUS 3. Computer Technology Group Templon, Dr. J.A. FOM B-Phys Tiecke, Dr. H.G.J.M. FOM ZEUS Akker, T.G.M. van den FOM Tilburg, Drs. J.A.N. FOM B-Phys. Antony, A.T. FOM Timmermans, Dr. J.J.M. FOM DELPHI Blokzijl, Dr. R. FOM Toet, Dr. D.Z. GSTOtherProjects Boterenbrood, Ir. H. FOM Tvaskis, Drs. V. VU HERMES Damen, Ing. A.C.M. FOM Uiterwijk, Ir. J.W.E. GST CHORUS Geerts, M.L. FOM Velthuis, Ir.J.J. FOM ZEUS Harapan, Drs. D. FOM Vermeulen, Dr.Ir. J.C. UVA ATLAS Hart, Ing. R.G.K. FOM Vavrik, Dr. D. FOM-HCM Other Projects Heubers, Ing. W.P.J. FOM Visschers, Dr. J.L. FOM Other Projects Huyser, K. FOM Visser, Drs. E. KUN ATLAS Joosten, Dr. Mw. K. Other Visser, Drs. J. FOM HERMES Kuipers, Drs. P. FOM Vos, Drs. M.A. UT ATLAS Leeuwen, Drs. W.M. van FOM Vreeswijk,Dr.M. FOM ATLAS Oudolf, J.D. QUADO Vries, Drs. G. de UU ANTARES Schimmel, Ing. A. FOM Vries,Dr.H.de FOM B-Phys. Steenbakkers, Ir. M.F.M. FOM Vulpen, Drs. I.B. van FOM DELPHI Tierie, Mw. J.J.E. FOM Wahlberg,Drs.H. UU B-Phys. Venekamp, Drs. G.M. FOM Wiggers, Dr. L.W. FOM ZEUS Wijk, R.F.van FOM Wijngaarden, Drs. D.A. KUN ATLAS Wilkens, Drs. H.G.S. FOM-KUN L-3 4. Electronics Technology Group Witt Huberts, Prof.Dr. P.K.A. FOM ANTARES Berkien, A.W.M. FOM Wolf, Dr. Mw. E.de UVA ZEUS Beuzekom,Ing.M.G.van FOM Woudstra, Ir.M.J. GST ATLAS Boer, J.de FOM Zihlmann, Dr. B. FOM-VU HERMES Boerkamp, A.L.J. FOM Born, E.A. van den FOM 2. TheoreticalPhysicists Es, J.T. van GST Bachetta, Drs. A. FOM-VU Evers, G.J. FOM Eynck, Dipl.Phys. T.O. FOM Fransen, J.P.A.M. FOM Fuster, Drs.Mw.A. GST Gotink, G.W. FOM Gaemers, Prof.Dr. K.J.F. UVA Groen, P.J.M. de FOM Gato-Rivera, Dr. Mw. B. GST Groenstege, Ing. H.L. FOM Heide, Drs. J. van der FOM Gromov, Drs. V. FOM Henneman, Drs. A. GST Haas, Ing. A.P. de FOM Holten, Prof.Dr. J.W. van FOM Harmsen, C.J. FOM Huiszoon, Drs. L.R. FOM Heine, Ing. E. FOM

108 Heutenik, B. FOM Brouwer, G.R. FOM Hogenbirk, Ing. J.J. FOM Bruijn, E.J. FOM Jansen, L.W.A. FOM Buis, R. FOM Jansweijer, Ing. P.P.M. FOM Ceelie, L. UVA Kieft, Ing. G.N.M. FOM Homma, J. FOM Kluit, Ing. R. FOM Jacobs, J. FOM Kok, Ing. E. FOM Jaspers, M.J.F. UVA Koopstra, J. UVA John, D. FOM Kroes, Ir.F.B. FOM Kok, J.W. FOM Kruijer, A.H. FOM Kuilman, W.C. FOM Kuijt, Ing. J.J. FOM Langedijk, J.S. FOM Mos, Ing. S. FOM Leguyt, R. FOM Peek, Ing. H.Z. FOM Mul, F.A. FOM-VU Reen, A.T.H. van FOM Overbeek, M.G. van FOM Rewiersma, Ing. P.A.M. FOM Petten, O.R. van FOM Schipper, Ing. J.D. FOM Rietmeijer, A.A. FOM Sluijk, Ing. T.G.B.W. FOM Roeland, E. FOM Stolte, J. FOM Römers, L.W.E.G. FOM Timmer, P.F. FOM Rövekamp, J.C.D.F. UVA Verkooijen,Ing.J.C. FOM Veen, J. van FOM Vink, Ing. W.E.W. FOM Wieten, P. FOM 7. Management and Administration Zwart, Ing. A.N.M. FOM Zwart, F. de FOM Berg, A. van den FOM Buitenhuis, W.E.J. FOM 5. Mechanical Engineering Group Bulten, F. FOM Cossee, Mw. N. Other Arink, R.P.J. FOM Doest, Mw. C.J. Other Band, H.A. FOM Dokter, J.H.G. FOM Boer Rookhuizen, H. FOM Dulmen, Mw. A.C.M. van FOM Boomgaard-Hilferink, Mw. J.G. FOM Echtelt, Ing. H.J.B. van FOM Boucher, A. FOM Egdom, T. van FOM Buskop, Ir. J.J.F. FOM Geerinck, Ir. J. GST Doets, M. FOM Greven-v.Beusekom, Mw. E.C.L. FOM Hover, Ing. E.P. FOM Heuvel, Mw. G.A. van den FOM Kaan, Ir. A.P. FOM Hooff, F.B. van Other Korporaal, A. FOM Kerkhoff, Mw. E.H.M. van FOM Kraan, Ing. M.J. FOM Kesgin-Boonstra, Drs. Mw. M.J. FOM Lassing, P. FOM Langelaar, Dr. J. UVA Lefévere, Y. FOM Langenhorst, A. FOM Munneke, Ing. B. FOM Lemaire-Vonk, Mw. M.C. FOM Riet, Ing. M. FOM Louwrier, Dr. P.W.F. FOM Schuijlenburg, Ing. H.W.A. FOM Mulders, Mw. P.N. FOM Snippe, Ir. Q.H.C. FOM Mors, A.G.S. UVA Thobe, P.H. FOM Pancar, M. FOM Verlaat, Ing. B.A. FOM Post, Mw. E.C. FOM Verschuijl, J.R. Other Rijksen, C. FOM Werneke, Ing. P.J.M. FOM Rijn, Drs. A.J. van FOM Zegers, Ing.A.J.M. FOM Rooij, Mw. T.J. La QUADO Spelt, Ing. J.B. FOM 6. Mechanical Workshop Visser, J. FOM Vries, W. de FOM Apel, A.W. FOM Woortmann, E.P. Other Berbee, Ing. E.M. FOM Beumer, H. FOM 8. Apprentices in 2001 Boer, R.P. de FOM Bron, M. FOM Aeijelts Averink, R.

109 Afework, Y. Gerritsen - Visser, Mw. J. Amasslam, M. Gulik, Ir. R.C.W. van Azouagh, Mw. S. Haan, M. Barisonzi, M. Heijne, Dr.H.M. Bobeldijk, A. Jarvis, Dr. P. Boer, Y.R. de Kruiper, H.A. Boezaart, T.J. Laan, Mw. F.M. Bruijn, R. Lutterot, Drs. M. Dalhuizen, J.M. Mangeol, Drs. D. Davidse, F. Melzer, Dr. O. Davidse, M. Middelkoop, Prof. Dr. G. van Demey, M. Mil, Drs. A. van Dirks, B.P.F. Muigg, Dr.Mw.D. Donders, R.S. Muijs Dr. Mw. A.J.M. Dongen, B.J. van Mulders, Dr. M.P. Fosse, D. Hadri, A. Noomen, Ir. J.G. Hagebeuk, J.C. Pesen, Dr. E. Hal, M.C. van Ploeg, F. Huiting, R. Reid, Dr. D.W. Hulsman, M. R¨omers, L.W.E.G. Jansen, F.M. Schalm, Dr. K.E. Jeukens, S. Sichtermann, Dr. E.P. Kappert, Mw. L. Trigt, J.H. van Kop, A. Tuning, Dr. N. Krijger, Mw. E. Ven, Drs. P.A.G. van de Kruijtzer, G.L. Yndurain, Dr. F. Lim, G. Zupan, Drs. M. Mejdoubi, K. Nat, P.B. van der Nijenhuis, Mw. N. Oudolf, H. Pronk, M. Rantwijk, J. van Schouten, S.S. Silkens, I.M.A. Snoek, H.L. Spoor, V. Tascon Lopez, D. Timmer, R. Vliet, E. van Vogelvang, M.

9. They left us

Adamus, Dr. M. Agasi, Dr. E.E. Amaryan, Dr. M. Bakker, C.N.M. † 30/7/01 Batenburg, Dr. M.F. van Bouhali, Dr. O. Brammerloo, A.V. Buijs, Prof.Dr. A. Buis, Drs. E.J. Buskens, J.P.M. Derrick, Prof.Dr. M. Geerinck, Ir. J. Duinker, Prof.Dr. P.

110